【单选题】Tom sits ____ the classroom while John sits ____ the room. [ ]
A.
in front of; at back of
B.
in the front of; at the back of
C.
in front of; at the back of
D.
in the front of; at back of
【简答题】(13分)现有下列短周期元素性质的相关数据: ① ② ③ ④ ⑤ ⑥ 原子半径(10-10m) 1.30 0.82 0.99 1.11 0.90 1.18 最高或最低化合价 +2 +3 +7 +4 +2 +3 -1 -4 请回答下列问题: (1)②和③形成的化合物类型为 (填“离子”或“共价”)化合物; (2)元素①的金属性比元素⑥要 (填“强”或“弱”),试从原子结构方面解释其原因: ; (3)...
【单选题】______ Chicago is a beautiful city today, but ______ Chicago of the 1920s was a very dirty place.
【单选题】Since Chicago is north of Washington, and Washington is north of Charleston, Chicago is north of Charleston.
A.
Chicago is north of Washington. Washington is north of Charleston. _____________________________ ∴ Chicago is north of Charleston.
B.
Chicago is north of Charleston. Washington is north of Charleston. ____________________________ ∴ Chicago is north of Washington.
【单选题】Sandy sits in front of Amy, but behind Simon. So Sandy sits ______ Amy ______ Simon. [ ]
【单选题】One's first impression of Chicago may be ______.