Mendel Carried Out Monohybrid Crosses with His Peas

Multiple Choice

Mendel carried out monohybrid crosses with his peas. What does that mean?

A) He planted each generation of peas in a cross-like formation so they could easily cross-fertilize.
B) The peas only had one trait.
C) The parent generation was crossbred or hybridized.
D) He was only looking at a single trait at a time in each experiment.
E) The alleles in the peas each determined multiple traits.