The answer is B. hairy stems (dominant).
If:
H - the dominant allele for hairy stems,
h - the recessive allele for non-hairy stems,
then:
HH - dominant homozygote with hairy stems,
Hh - heterozygote with hairy stems,
hh - recessive homozygote with non-hairy stems.
In autosomal dominant traits, the phenotype is
present if both copies of the dominant allele (H) are present (homozygous
individuals HH) or only one copy of the dominant allele is present
(heterozygous individuals Hh).
In this case all of the batch of tomato plants were heterozygous individuals Hh with hairy stems:
Parental generation: HH x hh
F1 generation: Hh Hh Hh Hh
