A plant with a white flower was crossed with a plant with red flowers. All of the offspring had pink flowers. Which of these terms describe the red flowers color trait?

Go online and look up ressesive and dominate Gene's and Gregory Mendel he crossbreed plants such as what you have described and have found some interesting results that do include your red and white crossbreeding to create pink. this is usually called a Punnet Square.

dominate gene

Red = R

White = W

recessive gene

Red=r

White = w

pink is either a mixture of recessive and dominant Gene's or one dominant and one recessive