在底模拆除时，对混凝土的强度有一定的要求．当板跨度＞2m且≤8m时，板构件达到设计的混凝土立方体抗压强度≥50%。( )

A bowline is used to（）.

A.join lines of equal size

B.form a temporary eye (loop) at the end of a line

C.be a stopper

D.keep a line from fraying