目前认为肌肉注射丙种球蛋白后，其临床效果有（）

A.对麻疹病毒感染可获得完全保护，但为时暂短

B.对甲型肝炎有较好的预防效果，但应早期应用

C.对先天性无球蛋白症和获得性丙种球蛋白低能状态者有防止细菌感染的较好疗效

D.儿童每月注射1次丙种球蛋白可有效地预防各种感染

E.预防艾滋病

What would be the impact on a firm’ s return on assets ratio (ROA) of the following independent transactions, assuming ROA is less than one Transaction 1: A firm owned investment securities that were classified as available-for-sale and there was a recent decrease in the fair value of these securities. Transaction 2: A firm owned investment securities that were classified as available-for-trading and there was recent increase in the fair value of the securities. Transaction 1 Transaction 2（）① Higher Lower ② Higher Higher ③ Lower Higher

A. ①

B. ②

C. ③