A.1/3樁長(zhǎng) B.1/2樁長(zhǎng) C.2/3樁長(zhǎng) D.3/5樁長(zhǎng)
A.≥30mm B.≥40mm C.≥50mm D.≥60mm
A.2倍 B.2.5倍 C.3倍 D.3.5倍