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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I would say that La Nina is responsible for dry conditions in California and typically it is the year after La Nina that the dryness turns often to severe drought. Drought can be bad for agriculture requiring a lot more irrigation and posing a drain on water resources which decrease also during a drought,
The pH of pure water is 7.0, which is neutral.
For a pH below this, the water is acidic. Substances that are acidic are often corrosive and thus could cause weather damaging. The pH of the precipitation in NY is below that of the precipitation in IL, and NY receives more precipitation, so for both of those reasons, it is likely to have more chemical weathering.
It was named the Qumran seas scrolls.
D. the student's conclusion shows experimental bias