Answer:
Heterozygous
Step-by-step explanation:
A pure breed (homozygous) plant that is dominant will have the following genotypes: AA
A pure breed (homozygous) plant that is recessive will have the following genotypes: aa
When you cross these two plants their offspring will all be heterozygous having the genotypes Aa
But the offspring plants (F1 generation) will all display traits of the dominant plant bacause the traits of the recessive allele (a) is being masked by the dominant allele (A)