They must have been enjoying themselves there, or they______so long.A．can"t have stayedB．w

They are sweating all over. They ______ in the field.A．may beB．must have been workingC．cou

The difficulties facing these hikers stem from the bad weather they have been having.A．cli

The oil must have been used up,______the light went out.A．becauseB．forC．sinceD．as

There must have been someone who had informed the owner of the bathing center of the sudde

They have been living under the most appalling

They have been living under the most appalling