题目

______ you eat the correct foods ______ be able to keep fit and stay healthy.        A. Only if; will you                                     B. Only if; you will          C. Unless; will you                             D. Unless; you will 答案：A科学家推测的原始生命的形成过程是：（并注明形成条件）______-----＞______------＞______--＞______----＞______．