1.b This is an illusory conditional sentence that omits if: if the predicate part of an if sentence contains should, had or were, you can omit if, and then should, had or were appears before the subject. If you add if after this sentence, it is if. If you take the train, you will get there faster.

2.c deer single complex isomorphism, jewelry collective noun, jewelry.

3. when a refers to a sentence, the leading word can only be which or as, when the clause is at the beginning of the sentence, as, when the clause is after the main sentence, which. The reverse of this sentence is like this: the earth goes around the sun, and the sun.

as everyone knows