航空是指载人或不载人的飞行器在地球()的航行活动。
A.高空
B.大气层内
C.宇宙
D.大气层外
参考答案:B
Tom and I went boating yesterday. _______ had a good time.
A.We
B.They
C.She
D.It
下列哪种不是防腐剂()
A.苯甲酸及钠盐
B.三梨酸及钾盐
C.丁基羟基茴香醚
D.对羟基苯甲酯类
E.乳酸链球菌素