_____to nuclear radiation, even for a short time , may produce variants(变异体) of genes in human bodies.
He reads newspapers every day to keep himself _______ about what's going on in the world.
He wrote a letter to me _______ that his trip to Japan had been put off because of the bad weather.
_______ a satisfactory operation, the doctor believed the patient would recover from his illness very soon.
_______ a satisfactory operation, the patient recovered from illness very quickly.
.When I came in, I saw Dr. Li _______ a patient.