The science of medicine, _____ progress has been very rapid lately, is perhaps the most important of all the science.
. The person we referred to____ us a report tomorrow.
The person we spoke to ____ no answer at first.
You can never imagine what great difficulty I have _____ your house.
Before he went abroad, he spent as much time as he ____ English.
Mr. Wang made up his mind to devote all he could ____ his oral English before going abroad.