Your answers are
1:A
2:C
3:B
4:A
Answer:
A: A new blood test makes it easier-and safer-to detect concussions.
Explanation:
The main idea of the passage is A new blood test makes it easier—and safer—to detect concussions.
Notice the phrases question the use of and proposed an alternative way. They suggest that the main idea involves a possible solution to a problem. Here, the main idea is that the problem of detecting concussions without radiation could be solved by a simple blood test.
To emphasize the speakers realization about how quickly moods tend to continually change
