necessary,it is important,it has been decided,it is natural,it is urgent,it is desirable,it is imperative,it is unusual,it is appropriate,it is preferable,it is possible 构后的主语从句： It is requested tat Miss Cai (should)give a performance at the party.有人请求蔡小姐在会上表 演一个节目。 It is desired that we (should)get everything ready by tonight.希望一切在今晚准备好。 It is necessary that he (should)be sent there at once.有必要马上派他到那里去。 It is important that we close our ranks in the struggle 在斗争中紧密团结是很重要的。5  necessary, it is important, it has been decided, it is natural, it is urgent, it is desirable, it is imperative, it is unusual, it is appropriate, it is preferable, it is possible等结 构后的主语从句：  It is requested tat Miss Cai (should) give a performance at the party. 有人请求蔡小姐在会上表 演一个节目。  It is desired that we (should) get everything ready by tonight. 希望一切在今晚准备好。  It is necessary that he (should) be sent there at once. 有必要马上派他到那里去。  It is important that we close our ranks in the struggle. 在斗争中紧密团结是很重要的