When a neuron transfers an impulse to another neuron or to a muscle cell, what is that location that receives the impulse called? synapse /dendrite / receptor

Option B , Dendrite

Explanation:

The information through axon of one neuron is passed on to the dendrite of other neuron. Thus dendrites  are responsible for receiving nerve impulses from other cells. The place where a axon of one neuron meets the dendrite of other neuron or any other type of cell such as muscle cells is called synapse. Actually Synapse  is a gap between the axon and dendrite.

A  chemical called neurotransmitter released by the axon of one neuron passes through the synapse to bind to the dendrite of other neuron or cell. Thus, It is the dendrite that receives the impulse.  

you know they are heterozygous for a trait because they have it as jj or jj.