错选了B，实际上文段中提到All the recorded staple crops grown in western Africa were introduced from...，所以这个选项可以直接排除
A选项：会不会在米饭和yams被人知道之前有过其他的主食［说明可能农业社会早就开始了］
C选项：outside of是错误的，不讨论西非之外的情况
DE都不在讲主食，与结论无关
E. The habitat of black bears consists of terrain that is significantly more varied than that of the habitat of sloth bears.（与题干逻辑方向不符：变成加强，black bear领域更复杂都会自己走了，那么sloth bear领域更简单的，应该也会走了）
can，既可以描述主观可能性，也可以描述客观可能性。比如，可以说bird can fly, but you can't.
be able to，多用于人和有生物的能力，不用于描述客观事物的能力。 比如说，天能下雨也能下雪，it can rain and snow，但不能说，it is able to rain and snow。
be capable of可以同时描写人和物的能力，但多用于描写事物的能力。比如，the train is capable of carring 100 people.；I am capable of building up a plant for cars.有能力建立一个汽车工厂。
the ability to do sth，只能跟to do；the capability to do sth或of doing sth
（转）Point to discuss:
As per manhattanprep.c…-t7994-15.html
"what his father gave him are a few books."
Ron: "no, you would still write "is", because the subject of the verb is still what his father gave him, not a few books."
The subject here is “what is much more difficult to determine”
As per Manhattan SC guide this is called Sub Phrase and it is always singular.
large, integrated companies such as Bethlehem Steel (that) once conducted operations from mining at one end of the process to shipping at the other.companies在定语从句中作主语，that不可以省略。如果作宾语是可以省略的，如：I like the girl who stands there. I like the price you gave me.
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错选了B，实际上文段中提到All the recorded staple crops grown in western Africa were introduced from...，所以这个选项可以直接排除A选项：会不会在米饭和yams被人知道之前有过其他的主食［说明可能农业社会早就开始了］
C选项：outside of是错误的，不讨论西非之外的情况
DE都不在讲主食，与结论无关