Hefellasleepimmediatelylastnight;hemust________(be)verytired.
网状结构除存在于丘脑，主要位于
________tothepapersisrestrictedtoDefenseDepartmentpersonnelonly.
heteachertoldthemsincelight________(travel)fasterthansound,lightning________(appear)togobeforethunder.
1949年中华人民共和国的建立，标志着中国从半殖民地半封建社会进入_________。
