Themorewelookedatthepicture,________.
Somemoleculesarelargeenough________(see)undertheelectronicmicroscope.
Ifound________toanswerallthequestionswithinthetimegiven.
Onlywhenyouhaveobtainedsufficientdata________cometoasoundconclusion.
ComradeLi________beinBeijingbecauseIsawhimintownonlyafewminutesago.
Night________(fall),wehurriedhome.