Has any side defended their World Cup title worse than England have in this edition?

Is Mitchell Marsh the first Australian to have taken a five-for and also scored a century in the World Cup? asked Dechlan Brennan from Australia
Mitchell Marsh took 5 for 33 against England in Melbourne on his World Cup debut in 2015, and during the current tournament hit 121 against Pakistan in Bengaluru.

He is indeed the first Australian to do this double in the World Cup - and actually only three others have managed it overall. Shakib Al Hasan of Bangladesh has two centuries plus a five-for (all of them in 2019), while the Indian pair of Kapil Dev and Yuvraj Singh have one of each.

There are a few near misses, none of them by Australians: eight further players have scored a century and taken four wickets in an innings in World Cup matches, and there are also two - Jimmy Neesham of New Zealand and Kenya's Curtis Obuya - with a five-for and a highest score in the nineties.

Marco Jansen conceded 92 runs against Sri Lanka, but still finished on the winning side. Was this a record? asked Mirza Chowdhury from India
The lanky South African left-arm seamer Marco Jansen went for 92 in his ten overs against Sri Lanka in Delhi recently; his side still won by 102 runs. This is a record for the World Cup, beating Kevin O'Brien's 2 for 90 in Ireland's victory over Zimbabwe in Hobart in 2015. Mitchell Starc came close a few days after Jansen, with 0 for 89 as Australia narrowly beat New Zealand in Dharamsala.

In all ODIs, three bowlers have conceded more runs than Jansen but still finished on the winning side. Top of the list is the Indian medium-pacer Vinay Kumar, who went for 102 in just nine overs against Australia in Bengaluru in 2013-14. India still won by 57 runs, helped by Rohit Sharma scoring 209.

Dale Steyn took 2 for 96 as South Africa defeated Australia in Durban in 2016-17, while England's Jake Ball went for 94 in what turned out to be a comfortable victory over West Indies in Southampton in September 2017. Bhuvneshwar Kumar of India also conceded 92 in an ODI innings, against New Zealand in Kanpur in 2017-18.

In England's World Cup game against Afghanistan, all 22 players got off the mark. How rare is this? asked Dennis Clarke from England
Everyone in the match between Afghanistan and England in Delhi in this World Cup opened their account with the bat (in fact all 22 players scored at least 2). This was the 27th such instance in all one-day internationals, but the first time it has happened in the World Cup.

There's been just one instance of this in T20Is, in a low-scoring match between Ireland (127) and Nepal (111 for 9) in Al Amerat (Oman) in February 2022.

The Australian openers reached their hundreds off consecutive balls against Pakistan. Has this happened before? asked Ronald Kamphuis from Australia, and several others
David Warner and Mitchell Marsh reached their centuries against Pakistan in Bengaluru off successive balls from Mohammad Nawaz in the 31st over.

There are three known previous instances of this, one of them in the World Cup: in 2015 in Hobart, Kumar Sangakkara and Tillakaratne Dilshan of Sri Lanka reached three figures off successive balls from Scotland's Kyle Coetzer. It had earlier happened at the Docklands Stadium in Melbourne in August 2000 (Steve Waugh and Michael Bevan for Australia vs South Africa) and in Kolkata in December 2009 (Gautam Gambhir and Virat Kohli - his first international century - for India vs Sri Lanka).

This answer comes with the usual health warning that our database does not contain ball-by-ball details of most matches before 2002, so there may be some other instances before that.

Has any country made a World Cup defence worse than England's in this tournament? asked Nick Johnson from England
Well, the qualifying stage hasn't finished, so England might yet surprise us, although the maths is against them after the defeat by India. I'm sure there will be thousands of words written on the reasons the holders failed to perform this time.

As for previous poor defences of the World Cup, the limpest were mostly in the 1990s. Australia were the holders in 1992, and played all their matches bar one at home - yet finished fifth in the qualifying table and failed to reach the semi-finals. Pakistan won that one, but in 1996 went out in the quarter-final. They had also played most of their games at home, although the quarter-final loss to India was in Bengaluru. Sri Lanka were the victors that year, but in England in 1999 they won only two group games, and failed to qualify for the Super Six stage.

In 2011, defending champions Australia went out in the quarter-finals, beaten by India in Ahmedabad.

Apart from this, the champions have always reached the semi-final at least; West Indies (in 1979) and Australia (2003 and 2007) have successfully defended the title. If you want to do your own research, then this table is probably the best place to start.