火灾的发生有一定的规律性，人们只有掌握了规律，就能扑救火灾（）
参考答案：错
Was it in 1802 when he discovered his hearing problem _____ Beethoven realized that his future ______ in composing music?
A．that; lay
B．when; lay
C．which; laid
D．that; laid
一对夫妇均有酒窝，基因型分别是Bb和BB ，则子女基因型是（ ）
A．bb
B．Bb
C．B
D．BB或Bb
