—        the team finished most of their research work?—Yes, but the rest        rather difficult.

When ______ comes to research into heart disease and its effects on the body, we do not have adequate substitutes for the use of animals.

. He ____ in the north, but now he ____ here.

It is the discovery of Cao Cao’s tomb, _____ was made in Anyang, Henan province, ____ has received widespread attention．

---Whom would you rather ______ to Hainan for the holiday, Bob or Jack? ---- Maybe Bob.