关于副词again的位置

1.        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.

(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
            

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

正解给的答案是A，但我总觉得again在句中的位置应该放在动词venture以后才对。

查了张道真的书，有些副词是能放到动词前面的，如never，seldom等，但是没有提到again。

请高手们指点一下。另外我觉得D中除了that is累赘一点，从语法上没什么错误吧？