题目

Teachers’ Day is a time to be________to all teachers who deserve special recognition. A．available                          B．grateful C．generous                            D．ridiculous 答案：B夏天冰棒周围冒“白气”与冬天人呼出的“白气”，下列说法中正确的是A.都属于汽化现象B.都属于液化现象C.一个是汽化现象，一个是液化现象D.一个是升华现象，一个是液化现象