How long ________ they ________ (dig) the ditch?
have … been digging
暂无解析
Herefusedtotelluswhetherhe________(undertake)thejob.
Thefloordoesnotlooksobadwhen________(sweep)clean.
Ihavebeenstudyinghereforfouryears,bynextsummerI________.
Wewerebusy________(get)thingsreadyforthetrialproductionwhenhephonedus.
Somemoleculesarelargeenough________(see)undertheelectronicmicroscope.