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