Sixteen outcomes could occur:

FFFF	FMFF	MFFF	MMFF
FFFM	FMFM	MFFM	MMFM
FFMF	FMMF	MFMF	MMMF
FFMM	FMMM	MFMM	MMMM

The reason b) is the correct answer is that they can be grouped. Here is a rearrangement of these outcomes in three sets:

All one kind:
FFFF MMMM

Three of one kind:
FFFM FFMF FMFF FMMM MFFF MFMM MMFM MMMF

Two of each kind:
FFMM FMFM FMMF MFFM MFMF MMFF

More Probability