Answer:
F1 generation
Step-by-step explanation:
As we have studied, during the start of Mendel's experimentation, he crossed true breeding plants showing one form of character with true breeding plant showing other form of a character. For example: A cross between true breeding tall plant with true breeding short plants resulted in the all tall offspring.
The F1 of first filial generation, he obtained from the cross between parents showed all dominant forms of traits in phenotype. For example: The offspring of those plants showed dominant traits and all recessive traits were masked due to the presence of dominant alleles. This is because dominant traits need only one dominant allele of the gene to be expressed, however recessive traits need two recessive alleles of the genes to be expressed. Please see the attached picture for better understanding.
Hope it help!