I’m also stuck on this question
Answer:
studies show that solar variability has played a role in past climate changes. For example, a decrease in solar activity is thought to have triggered the Little Ice Age between approximately 1650 and 1850, when Greenland was largely cut off by ice from 1410 to the 1720s and glaciers advanced in the Alps.
Explanation:https://climate.nasa.gov/causes/
Answer: A
Explanation: By putting the term and its abbreviation once, the reader will then understand what the abbreviation stands for and the writer can use it in the text without the reader being confused.