140. It may be another fifteen years before spacecraft from Earth again venture to Mars, a planet now known to be cold, dry, and probably lifeless.B

(A) again venture to Mars, a planet now known to be

(B) venture to Mars again, a planet now known for being

(C) will venture to Mars again, a planet now known as being

(D) venture again to Mars, a planet that is known now to be（A）

(E) will again venture to Mars, a planet known now as being

我选了B。。答案是A。

哪位NN讲一讲，be known to be,be known as, be known for being 之间的区别

sth1/sb be known as sth2/sb

例如：Many people knew him as a local businessman. = He was known as a local businessman by many people.

sth1/sb be known to do sth2

例如：Smoking is known to increase a person's risk of developing lung cancer.

sth1/sb be known to be sth2/sb

例如：本句A

be known for表达的是对物体或人物特性的辨识

例如：I knew him for a liar.我看得出他是个骗子。= He was known for a liar by me. －不过，需要指出的是，这种结构在语法的正确答案中好像从没出现过，我们一般只强调know as / know to do这两种结构。

补充一点

know for sth. 没有know for doing sth.