15. LACE w:st="on">MadagascarLACE> was one of the last habitable areas of the earth to undergo human settlement, which has made it an ideal site for researching rare flora and fauna.

(A) Madagascar was one of the last habitable areas of the earth to undergo human settlement, which has made it

(B) Madagascar was one of the last habitable areas of the earth to have undergone human settlement, and that has made it and that

(C) Madagascar underwent human settlement as one of the last habitable areas of the earth, which makes it

(D) LACE w:st="on">MadagascarLACE>, one of the last habitable areas of the earth, underwent human settlement, making it（E）

(E) Because LACE w:st="on">MadagascarLACE> was one of the last habitable areas of the earth to undergo human settlement, it is

答案是E,我认为D是认的啊,而且E中的Because是怎么体现出来的啊,没看出有因果?