This question should be clarified a bit to say how many workers are there. Otherwise both true and false can be correct. If there are less workers then maps which are running at given moment will be less. Otherwise if more or equal workers are available then all can run.

The question is wrong IMHO. Number of workers is totally independent on number of data partitions. You can have mn.

The question should be "the number of workers is typically...", "you can have M workers", "you must have at least M workers", "you can't have more than M workers", "if you have M workers, you get better performance than M/2 workers" or something like that...

Empty Editorial, seriously??

False. There are generally less worker nodes than partitions

very nice for beginner of given domain