37.You must clean this machine before it is used.   A. This machine is cleaned before it is used.   B.This machine will be cleaned before it is used.   C.This machine is being cleaned before it is used.   D.this machine must be cleaned before it is used. 38.People believe that he has special knowledge which may be useful to the police.   A.He is believed to have special knowledge which may be useful to the police.   B.He was believed to have special knowledge which may be useful to the police.   C.He has special knowledge which may be useful to the police.   D.He has special knowledge which may be useful to the police is believed. 39. People don’t use this road very often.   A.This road is not used very often.   B.Not very often this road is not used.   C.This road very often is not used.   D.This road not very often is used. 40. “ Where should I go for the next holiday?” Linh said   A.Linh asked me where she should go for the next holiday?   B.Linh had no idea where to go for the next holiday.   C.Linh advised me to go somewhere for the next holiday.   D.I asked Linh where I should go for the next holiday?