A. 左右两壳不对称,固着壳大 B. 成体足退化或消失 C. 贝壳较厚,表面有棘、刺等 D. 有发达水管,且感官发达
A. Φ48×3.5或Φ51×3 B. Φ38×3.5 C. Φ30×3.5 D. Φ55×3.5
A. 2 B. 3 C. 4 D. 5
A. No, I already have plans. B. I'd love to, but I'm busy tonight C. No, I really don't like being with you D. I'm ill, so I shouldn't go out.