A. 0.12 (mol/L)/s
rate = 1 x 10-2 • 2^2 • 3
The simple trick which one can consider in such problem where it is asked for positron emission is :
<span>When the atomic number goes DOWN by one and mass number remains unchanged, then a positron is emitted.
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<span>a. </span>

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Here the atomic number decreases by one.
Similarly, options b and d are eliminated.
Option c is also not the answer.
For c, Count the atomic number on left side and compare it with right side. You will see it is 9 on left and 8 on right. Atomic no. did go down by 1. But the atomic mass is changed as well.
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In magnet I believe nickle is used most often
Answer:
it causes alot of harm to the earth.
Explanation:
earthquakes
an so on