Answer:
a. all tall
Explanation:
If genotypically one of the parents is homozygous dominant and another one is heterozygous for plant height then phenotypically all their progeny will be tall.
Let us suppose, 'T' represents dominant allele and 't' represents recessive allele. Then the genotype of one parent who is homozygous dominant will be TT and genotype of another parent who is heterozygous will be Tt.
The cross is depicted in the attachment.
Here it may also be noted that genotypically two of the progeny will be homozygous dominant while two of the progeny will be heterozygous but phenotypically all the progeny will be 'tall'.
