A:N和2N
B:2N和3N
C:N、2N和4N
D:2N、3N和4N
雪上加霜____(A.在气温降到0℃以下时,接近地面空气中所含的水汽在地面物体上凝结成的白色冰晶 B.像霜的东西 C.比喻白色)
按图索骥____(A.搜寻 B.要、取)
Welcome to our charity show. It will be held _______ the night of May 4th.