The new varieties of plants are produced by

The correct option is A Selection and hybridization
As a part of agriculture, man started rearing plants and animals to meet his requirements. This is when humans started to learn how to influence the process of natural evolution, so as to breed plant or animals. Slowly and gradually, this process of expedited evolution, through selection and cultivation of plants, acquired the form of a routine endeavor called as plant breeding. In this, heredity, which refers to the passage of various characteristic features from the main plant (the parent) to the plantlets (the progeny), plays an important role. The effects of heredity had been apparent to early man and he had taken advantage of them ever since the advent of agriculture. Various methods have evolved in plant breeding.

One of the most important methods is that of selection. After the selection of parents with desired characteristics, they can be hybridized to yield better offsprings with both the parent characteristics.

So, the correct answer is 'selection and hybridization'