He studies hard all the time, _________ he has made rapid progress in many ways.
选择一项：
a. because
b. yet
c. so 解析：句意：他一直努力学习，因此他在许多方面取得了迅速的进步。A. so B. because C. but D. yet所以；因为；但是；仍然。前后两句话是一种因果关系，结合选项，可知A选项符合题意，故答案选A。
d. but