Question

Which answer shows all the like terms in this list 4x,1/2x,2y,4,x,3x

Answer 1

You haven't shared the answer choices.

Let's rewrite that first x term:  {4x, (1/2)x, 2y, 4, x, 3x), also leaving more space between the answer choices.

I see four x-terms in  { 4x, (1/2)x, 2y, 4, x, 3x } .  The like terms are {4x, (1/2)x, x, 3x }.  There are no other groups of like terms.