The split between humans and living apes is thought by some scholars ____ 15 to 20 million years ago.
More than two hundred years ago the United States _______ from the British Empire and became an independent country.
. ---Professor Wang is said ______ in New York. ---No wonder he knows a lot about America.
The games _______ the young men competed were difficult.
The young nurse was very nervous when she ______ the doctor in operating on the patient.
.— Are you satisfied with the result of the examination? — Not at all. _______.