3 . Be careful when you deal with this chemical, as it will explode when        to sunlight.

A．being exposed

B．to expose

C．exposing

D．exposed

4 . ______ in the early 20th century, the school keeps on inspiring the children’s love of art.

A．Found

B．Founding

C．Founded

D．Finding

5 . With dinner ________, my mother went on to water her vegetables.

A．had prepared

B．prepared

C．preparing

D．to prepare

6 . ________ in 1636, Harvard is one of the most famous universities in the world.

A．To found

B． Founding

C．Founded

D．Having been founded

7 . The earliest ______ recipes for making Lu date back to Qimin Yaoshu, an ancient Chinese agricultural text written in the 5th century.

A．preserving	B．being preserved
C．preserved	D．having been preserved

8 . There has been a dramatic rise in the number of extreme weather events over the past 20 years, ______ largely by rising global temperatures, according to a new report from the United Nations.

A．causing

B．caused

C．having caused

D．having been caused

9 . The disease, if ________ (treat) timely, can be cured.

A．treated

B．treating

C．have treated

D．to treat

10 . ________ with the weather in Beijing, the winter in Changchun is much colder.

A．Compare

B．To compare

C．Comparing

D．Compared