12. Chronic low-level leaking and the routine discharge of drilling mud and mineral salts present considerable environmental risk during offshore oil drilling. (A) Chronic low-level leaking and the routine discharge of drilling mud and mineral salts present considerable environmental risk during offshore oil drilling. (B) The reason offshore oil drilling presents a considerably environmental risk is because of chronic low-level leaking and the routine discharge of drilling mud and mineral salts. (C) A considerable risk to the environment is presented during offshore oil drilling, where low-level leaks are chronic and the routine discharge of mud and mineral salts. (D) Offshore oil drilling presents a considerable risk to the environment due to the fact of chronic low-level leaks, and mud and mineral salts are routinely discharged.（A） (E) Chronic low-level leaking, along with the routine discharge of drilling mud and mineral salts, are what make offshore oil drilling environmentally risky. 请问NN，A 中risk 不需要复数形式么？ E 错在哪里？ 其中are what make.. 这样的用法可以么？ | 
