Somemoleculesarelargeenough________(see)undertheelectronicmicroscope.
Wewerebusy________(get)thingsreadyforthetrialproductionwhenhephonedus.
Iknowitisn’timportantbutIcan’thelp________aboutit.
ComradeLi________beinBeijingbecauseIsawhimintownonlyafewminutesago.
heteachertoldthemsincelight________(travel)fasterthansound,lightning________(appear)togobeforethunder.
邮箱：