A:闭合S时,灯泡A慢慢变亮
B:当断开S时,灯泡A立即熄灭
C:当断开S时,灯泡A突然闪亮一下,然后逐渐熄灭
D:若把线圈L换成电阻,断开S时,灯泡A突然闪亮一下,然后逐渐熄灭
如图,AB是⊙O的直径,C是⊙O上一点,AD垂直于过点C的直线,垂足为D,且AC平分∠BAD.(1)求证:CD是⊙O的切线;(2)若AC=26,AD=4,求AB的长.
My father ____ (take) the bus to work every day.