Answer:
The correct answer is - can be explained by the law of dominance.
Step-by-step explanation:
In this experiment of Gregory John Mendel where he made a cross between a purebred tall plant and a purebred dwarf plant and in the first generation all the offspring were tall.
It can be explained by that every offspring get one allele from both parents and in purebred both alleles are either dominant or recessive and both parent plant gives one allele which makes a heterozygous condition in which the dominant allele masks the recessive allele and offspring express phenotype of the dominant parent.