TU是个两位数（T是十位数，U是个位数）。若TU等于T与U的乘积的2倍，那么U=（）。
参考答案：6
“两状态转变”模型
What is the normal length of anchor cable used to anchor a vessel?（）
A.An amount equal to the depth of the water
B.Two times the depth of water
C.Three to four times the depth of water
D.Five to seven times the depth of water
