Question

_to be most difficult,drill a is taken away from the lesson.

Answer 1

答案 Considered 是正确的, 没有必要用being considered.

Considered to be most difficult 是过去分词短语作原因状语, 其逻辑主语是句子的主语Drill A.

consider 与Drill A 为被动关系: "Drill A 被认为是非常难学的", 故用过去分词短语作状语.

实际上, Considered to be most difficult 相当于省略的原因状语从句.

Considered to be most difficult =Since Drill A is considered to be most difficult .

当状从的主语与主句的主语相一致, 且从句中含有be动词时,

就可省略从句中的"主语+be动词"及状从的连词.

因此, Since Drill A is considered to be most difficult 省略Since Drill A is 之后

就成了Considered to be most difficult .

而being considered虽然也是表示被动, 但是它表示的动作与谓动的动作同时发生.

翻译成汉语就是: "Drill A 正在被认为是非常难学的", 这显然不通,故不能用being considered.