What fraction of u. s. physicians out of total physicians are specialists and subspecialists?

Only 1/3 of US doctors are specialists and subspecialists.

Explanation:

An expert doctor is one who works with a specific field of medicine (such as an endocrinologist who deals only with hormonal issues, for example). A subspecialist doctor is another doctor who specializes in some organ or, what is often occurring, some specific disease.

This type of professional requires a long time of study and a great economic expense with the academic specialization, therefore, there are fewer specialist doctors and subspecialists than genealogical doctors, as general practitioners, who although they study a lot, can practice the profession in a shorter time period. It is estimated that only 1/3 of doctors in the US are specialists and subspecialists.

tissue

explanation:

it is actually formed by geoup of cells which is tissue

i would say it is