Answer:
d. the atomic number remains the same.
Explanation:
First at all it's important to know how to read nuclear information

X is the atomic symbol, A the mass number and Z the atomic number of the element.
Gamma rays emitted on gamma decay are characterized as 
If we write the nuclear equation for the decay, we have that:

The sum of the mass numbers and atomic numbers on the right side has to be equal to the left side numbers of the equation, that means the mass number and the atomic number remains the same for the resulting atom to preserve the equality.
The time period of the pendulum is affected by the acceleration due to gravity. The tension does not have any effect on the time period of the pendulum and also the mass of the bob does not effect the time period of the pendulum.

Hence, if the gravity increases then the time period of the pendulum will decreases and it will swing faster.
Answer:
3.round object that orbits the Sun but lacks the ability to clear the neighborhood around its orbit.
Explanation:
in 2006 the IAU, said that a dwarf planet is round object that has not cleared the area round a object and that is why Pluto, Ceres, and Eris are dwarf planet.
The horizontal force : f = k*N
k- coefficient of friction
k = f /N
N = m * g = 45 kg * 9.81 m/s² = 441.45 N
k = 25 N : 441.45 N = 0.057
Answer C) 0.057
Answer: D
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X: positive
Y: negative
Explanation:
It's either A or D and I chose A and got it wrong.