Answer:
D
Explanation:
Double the first equation. Write the second below it. Rearrange the second.
2x - 20 = - 4y
<u>-2x -16= +4y</u> Add.
- 36 = 0
There is no solution to this pair of equations.
Answer:
A. Systematic
Explanation:
it is because he ask each student in that particular class, so that he question them in a systematic way.
Explanation:

An outcome measured to see the effectiveness of the treatment.

The variable that is changed or manipulated in a series of experiments.
Hope it helps!
Answer:
D: It explains how much ocean water levels have changed from the past to the present.
Explanation:
The passage states that "At the coldest part of the Ice age, the seas were about 410 feet(125 m) lower than the today. As carbon dioxide levels in the atmosphere naturally rose, Wanless explains, glaciers melted, and the seas rose hundreds of feet." Those two sentences from the passage centrally describe information about the sea and how it has changed throughout the years. Therefore, the answer is D: It explains how much ocean water levels have changed from the past to the present.
Plates at our planet's surface move because of the intense heat in the Earth's core that causes molten rock in the mantle layer to move. It moves in a pattern called a convection cell that forms when warm material rises, cools, and eventually sink down. As the cooled material sinks down, it is warmed and rises again