Answer:
a) Addition reaction, is your answer
Answer: Transition from X to Y will have greater energy difference.
Explanation: For studying the energy difference, we require Planck's equation.

where, h = Planck's Constant
c = Speed of light
E = Energy
= Wavelength of particle
From the equation, it is visible that the energy and wavelength follow inverse relation which means that with low wavelength value, energy will be the highest and vice-versa.
As electron A falls from X-energy level to Y-energy level, it releases blue light which has low wavelength value (around 470 nm) which means that it has high energy.
Similarly, Electron B releases red light when it falls from Y-energy level to Z-energy level, which has high wavelength value (around 700 nm), giving it a low energy value.
Energy Difference between X-energy level and Y-energy level will be more.
Answer: D) The effect of gravity on an object
Explanation: We're not talking about mass, we're talking about weight. Weight is measured by the force of gravity on a object. For examples, you might be 100 pounds on Earth but 12 pounds on the moon.
Answer:
C. Arsenic
Explanation:
Each period is terminated by a noble gas with a closed valence shell with electronic configuration ns²np⁶. Since noble gases have completely filled orbitals in the valence shell and are very stable, it becomes very difficult to alter their stable arrangement by the addition or removal of electrons. They they exhibit very low chemical reactivity
Noble gas elements are: Neon, Argon, Krypton, Xenon, Radon, Helium (2 electrons in outer shell, stable).