We’ve booked a room in the centre of town for the guests _____ they can stay for three days.

A．when

B．whom

C．which

D．where

对职工接触有害因素与职工可能发生损害的关系，属何种类型调查（）

A．横断面调查

B．队列调查

C．病例－对照调查

D．普查

E．职业病体检