A smaller shell opening that restricts mobility and ingestion relative to that of a snail of the commoner form.
In this sentence, I cannot understand it very well. So, here is what I comprehension of this sentence, a smaller shell opening restricts mobility and ingestions, and the mobility and ingestion of a snail of the commoner form does not restrict or less restrict, am I right?
Would this help?
21．这题居然是类比，SIGH。。。居然没有看出来，根据题干要求，答案要符合两点：1。关于形态结构特 征 2。必须是缺点，就是左右是不一致镜象。A不符合2，B不合1，C不合1，D是不合2，只有E的 a smaller shell opening是合A，restricts合B，所以答案是E（以上为杨继的阅读分析解释：P