矿物药中含有()问题使得矿物药的使用一直备受争议—（）
A重金属
B微量元素
C化学成分
D碳酸钙
When was the building being visited constructed？
About twenty years ago.
B. In the sixteenth century.
C. From the late 1800s to the early 1900s.
D. From the late 1600s to the early 1700s.
Which of the following is INCORRECT？
A. The Internet can be connected by light waves.
B. You can pay many different kinds of bill online.
C. Most of universities offer classes on the Internet.
D. You can even buy groceries online at online stores.
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