The half life of a radioactive element is the time needed to the element to decay and reach the half amount of the initial amount. Here we have a radioisotope element which decays its half from 10,000 to 5,000 in two days. Therefore, its half life is 2 days.
Actually Welcome to the Concept of the Astrophysics.
Let's categorize them eventually ==>
1.) Earth ==> 1.) travels around the Sun
2.) takes 365.25 days .
2.) Moon ===> 1.) travels around the Earth
2.) Takes 27.3 days.
<u>Answer: </u>The correct answer is Option b.
<u>Explanation:</u>
Oxidizing agent is defined as the chemical reagent which helps the other chemical compound to get oxidized and itself gets reduced. The oxidation state for these species gets reduced because they are undergoing reduction reaction.
For the given chemical equation:

Oxidation state of Chromium is getting reduced from +6 to +3 and oxidation state of chlorine getting increased from -1 to 0.
Hence,
acts like and oxidizing agent because it is itself getting reduced to 
Therefore, the correct answer is Option b.
Answer:
New pressure P2 = 4.95 atm
Explanation:
Given:
Old volume V1 = 1.50 L
New volume V2 = 0.50 L
Old pressure P1 = 1.65 atm
Find:
New pressure P2
Computation:
P1V1 = P2V2
So,
(1.50)(1.65) = (0.50)(P2)
New pressure P2 = 4.95 atm
Mechanical twinning occurs in metals having body center cubic and hexagonal closed packed structures. Twinning is said to occur when a portion of a crystal takes up an orientation that is related to the orientation of the untwinned lattice in a definite symmetrical manner.