Order of a paragraph

I have one more question.

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Above your wrist is a point you can press into medical service to relieve nausea.

(A) Find the groove (long, narrow channel) between the two large tendons on the inside of your wrist that rum from the base of the pain up to the elbow.

(B) About 2 inches above the wrist, press down hard with a thumb or finger for a minute.

(c) Six studies confirm the effect, although why it works is still unclear.

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The question is to choose the right order after the 'blue' colored sentence.

(1) a-b-c

(2) b-c-a

(3) b-a-c

(4) c-a-b

(5) c-b-a

The answer is (4). But I think (1) is also possible.

The answer says that the word ( the effect) is connected to 'to relieve nausea.' So, (4) is the only solution.

Help me please..