PGO waves occur at a rate of approximately ___________________.
 | |
 |
5 to 7 times per second; |
 |
1 time per second; |
 |
1 Hertz; |
 |
2 to 4 times per second; |
 |
both alternatives b and c are correct; |
INCORRECT - PGO waves occur at a rate of 1 per second.
[Review Part 1 of the tutorial] [Review Part 2 (Matching) of the tutorial]