Reading books ________ a bridge between our lives and the unknown world．（ ）
| A． |
built |
B． |
build |
C． |
builds |
The old building ______ down to make room for the city library a year ago．（ ）
A．was takingB．is takenC．was takenD．would take
Look，______ excited the boy is on seeing these cute pandas!（ ）
A．howB．how anC．what anD．what
Where is your uncle，Jane？
He is in Guangzhou．He ______ for a month．（ ）
A．has leftB．has gone
C．leftD．has been away
Chinese people find ______ our duty to help develop African countries along the Belt and Road （一带一路）．（ ）
A．itB．thisC．thatD．these
______ riding shared bikes（共享单车） is an environmentally friendly way to travel，many of the bikes are thrown everywhere．（ ）
A．AlthoughB．AsC．UnlessD．Until