The diameter of a circle extends from one side to the other.

• A (The phrase "extends from one side to another" is incorrect; it should be "extends from one side to the other.")

Because of the power outage, we could not videotape the game.

• B (The correct phrase should be "Because of the power outage.")

During my studying period, I consulted the adviser about my schedule.

• A (No correction needed; the sentence is acceptable as is.)

In the outskirts of the town, there are several parks.

• C (The phrase "several parks" is not incorrect, but could be improved by specifying the number of parks.)

In spite of the heat, band practice continued through the afternoon and into the evening.

• C (The phrase "In spite the heat" is incorrect; it should be "In spite of the heat.")

In the fifties, people danced to the music of the big bands.

• A (The phrase "people dance" should be corrected to "people danced.")

The blue of the sea stretched to the horizon like a picture with a red sun setting.

• C (The phrase "like a blue picture with a red sun highly above" is incorrect; it should be "like a picture with a red sun setting.")

Without a guide, white-water rafting can be fatally dangerous.

• D (The phrase "can be fatal dangerous" should be corrected to "can be fatally dangerous.")

Snorkeling is good in the shallow waters around coral reefs.

• C (No correction needed; the sentence is acceptable as is.)

At the beginning of summer, we had the builders add a porch to the rear of our house.

• B (The phrase "had the builders add" is acceptable, but could be improved to "had the builders construct.")