Chất tác dụng với dung dịch HCl tạo thành chất khí nhẹ hơn không khí là:

A. Mg 

B. CaC O 3

C. Cu 

D. N a 2 S O 3

Tuổi sinh thái là:

A. tuổi thọ tối đa của loài.

B. tuổi bình quần của quần thể.

C. thời gian sống thực tế của cá thể.

D. tuổi thọ do môi trường quyết định.

Choose the letter A, B, C or D to answer these following questions

A new study published in the journal Science shows definitive evidence of organic matter on the surface of Mars. The data was collected by NASA's nuclear-powered rover Curiosity. It confirms earlier findings that Mars, the Red Planet once contained carbon-based compounds. These compounds – also called organic molecules – are essential ingredients for life as scientists understand it.

The organic molecules were found in Mars's Gale Crater, a large area that may have been a watery lake over three billion years ago. The rover encountered traces of the molecule in rocks extracted from the area. The rocks also contain sulfur, which scientists speculate helped preserve the organics even when the rocks were exposed to the harsh radiation on the surface of the planet.

Scientists are quick to state that the presence of these organic molecules is not sufficient evidence for ancient life on Mars, as the molecules could have been formed by non-living processes. But it's still one of the most astonishing discoveries, which could lead to future revelations. Especially when one considers the other startling find that Curiosity uncovered around five years ago.

Question: Have there been enough evidences to confirm the existence of life on Mars?

A. Yes, there have

B. No, there haven’t

 Chính quyền Trung ương dưới thời Nhà Nguyễn được tổ chức theo mô hình thời nhà nào trước đó?

A. Thời Nhà Lý

B. Thời Nhà Trần

C. Thời Nhà Hậu Lê

D. Câu A và B đều đúng