预防儿童视力残疾的关键是()。
A.注意优生优育
B.早期发现和治疗弱视
C.积极预防白内障
D.预防眼外伤的发生
E.及时治疗各种眼病
参考答案:B
Some students think English is very difficult _____ it's very interesting, [ ]
A. then
B. or
C. and
D. but
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