The answer is c. number of protons and d. atomic number. The proton number can identify an element. And also the atomic number is equal to the number of protons.
Answer:
lighting a match is the answer.
Newton's third law of interaction, says that if one body exerts a force on a second body, the second body exerts a force equal in magnitude and opposite in direction on the first body. It's the law of action-reaction, and it helps to explain why you feel a jolt when you collide with another bumper car.
Answer : At constant pressure work is done by the system on the surroundings.
Explanation :
Work done : Any quantity that flows across the boundary of a system during a change in its state and it completely convertible into the lifting of a weight in the surroundings.
Formula for work done is:

Sign convention :
- When volume expand then system work that means work done by the system.
w = (-ve)
- When volume compress then surrounding work that means work done on the system.
w = (+ve)
The given reaction is:

This is a evaporation process in which phase changes from liquid state to gaseous state at constant temperature.
At constant pressure, work depends only on volume.
In evaporation process, the volume expand that means work is done by the system on the surroundings.
Sign convention is, w = (-ve)
Thus, at constant pressure work is done by the system on the surroundings.
Answer:
Your answer is Gravity,
The Earth's gravity pulls things at a rate of 9.8m/s² (varying depending upon one's distance). according to Newton, "all mass in the universe exerts some gravitational force". you are pulling on Sagitarios A* (the black hole at the center of the milky way galaxy) right now, and it is also pulling on you.
If you have any questions I <em><u>insist</u></em> that you ask in the comments.
<em>Wbob1314</em>