Gregor mendel raised and observed pea plants. in his observations he noticed that some pea plants were tall and some were short. some plants produced round peas and some produces wrinkled peas. mendel noticed that different combinations of these traits occurred in each generationwhat is the best explanation for this variation in pea plants

Due to presence of dominant and recessive trait

Explanation:

Mendel in his experiment found that when he crossed a true breeding pea plant (TT) with a true breeding short pea plant (tt), then all the first generation offspring were tall (Tt). However, in second generation, short pea plant reappeared.  

Form this, he devised that allele for specific trait like tallness “T” is dominant over recessive trait i.e “t” as when these two allele occur together the characteristic of “t” are not expressed. In fact, a recessive allele like “t” will occur only when they are in pair i.e tt