The correct option is A Selecting a breed which is leaner
The term breed refers to a set of animals which closely resemble each other in certain marked features by descent.
A scientific process of mating selected individuals to produce offspring with desirable characteristics is called controlled breeding (mating).
Selecting a breed which is leaner is not preferred as it usually has poor milk producing capacity. Leaner breeds also do not produce enough meat. . So, option a is incorrect.
Milk yielding capacity is highly dependent on quality of breed. So, option d is correct.
Shifting from conventional to controlled breeding helps in customizing the quality (such as disease resistant) and quantity (such as high yielding) of the produce obtained. So, option b is correct.
Hybrids developed by controlled mating usually have high milk yielding potential. They are also disease resistant and hence are easy to maintain. So, option c is correct.