It's a good question.

It's a bit shocking to see that so far out of just over 600 people about 55 people picked the non-existent and utterly implausible DBCC CHECKCACHE, and about 175 picked the equally non-existent although less implausible sounding DBCC CHECKFILEGROUP; and it seems amazing that about 120 people thought that DBCC CHECKIDENT was something that DBCC CHECKDB would do. So I hope that people will learn from this question.