在硫酸铁溶液中,加入a g铜,完全溶解后,又加入b g铁,充分反应后得到c g残余固体,且b<c,则下列判断正确的是
Edward, you play so well. But I ______ you played the piano.
She brought with her three friends, none of ______ I had ever met before.
I tried phoning her office, but I couldn’t _______.
His sister left home in 1998, and _______since.
What do you mean, there are only ten tickets? There _____ be twelve