A.先場(chǎng)底后邊坡 B.先邊坡后場(chǎng)底 C.先場(chǎng)中后四周 D.邊坡場(chǎng)底同時(shí)鋪
A.60° B.55° C.50° D.45°
A.2 B.3 C.4 D.5