非接触式密封严密性较好,适用于较高速度。()
参考答案:对
“You must find such long hours very tiring.” “______. I enjoyed it.”
A.After all
B.Never mind
C.Not in the least
D.That’s all right
将一枚质地均匀的一元硬币抛3次,恰好出现一次正面的概率是______.