If an H is for tall trait which is dominant and h is the recessive trait for short, which of the following crosses will result in 1:1 tall:short progeny (offspring).

A) HH Xhh
B) hh X hh
C) Hh X hh
D) Hh X Hh

The cross that guarantees a height trait ratio in the offspring of 1 : 1 high/low is Hh X hh (option C).

Explanation:

For a characteristic such as size, where tall (H) is the dominant trait and short (h) is the recessive, the crossing of a tall heterozygous (Hh) individual with a short one will have a probability that half of the offspring will be tall and the other half short.

This can be demonstrated with a Punnett square:

Cross Hh X hh

Alleles      H      h

h              Hh    hh

h              Hh    hh

Based on this result, half of the offspring will be tall, with genotype Hh, and the other half short, with genotype hh, which corresponds to a tall : short ratio of 1 : 1.

In the other options is not possible to obtain this result:

A) HH Xhh  = 100% Hh.

B) hh X hh  =  100% hh.

D) Hh X Hh = 50% Hh, 25% HH and 25% hh.

the answer to your question is:

c. complementary base-pairing