The correct answer is (A).
Getting to the Answer: To determine how many times a geomagnetic storm occurred between 1994 and 2007, use the Figure to identify when the Ap was greater than or equal to 30 nT. According to the Figure, the maximum Ap in that 13-year period was approximately 22 nT, which is below 30 nT. Thus, a geomagnetic storm did not occur in that 13-year period.
(A) Correct: this matches the analysis above; the Ap shown in the Figure was never greater than or equal to 30 nT
(B) Incorrect: at no time during the 13-year period shown in the Figure did the Ap equal or exceed 30 nT for a geomagnetic storm to occur
(C) Incorrect: at no time during the 13-year period shown in the Figure did the Ap equal or exceed 30 nT for a geomagnetic storm to occur
(D) Incorrect: at no time during the 13-year period shown in the Figure did the Ap equal or exceed 30 nT for a geomagnetic storm to occur
Spacing out study makes it stick. Get practice questions emailed to you every day.