洗肉水样血便提示
A.瘀点B.充血性皮疹C.瘀斑D.血肿E.小红痣
参考答案:D
Hard as a teacher may try, he can't ____ to make all his students make a difference in study, letting alone in life. [ ]
A. ensure
B. be sure
C. guarantee
D. insure
生物对污染物的抗性机制是外部排斥的结果。