The force that attracts all matter to each other is gravity, i believe.
Answer: <u><em>D. An observation that has a number associated with it</em></u>
Explanation: The answer is D. An observation that has a number associated with it. I would explain further, but it is pretty self explanatory.
<em>Good luck!</em>
The most suitable option for the first question is definitely <span>stratus clouds which usually stratch over the sky creating overcasts.
The next one should be </span><span>nimbus, as they dark and usually help to predict the storm.
And the last one </span>cumulonimbus that point on thunderstorms and so on.
Adjustment knobs are used to focus light in a light microscope