(1)It was December 7, 1941.

(2) The freighter Florentine, 320 miles northeast of the Hawaiian Island of Hilo was lumbering along at about 15 knots when the garbled message came in over the radio:

(3) “Attack on Pearl Harbor; This is not a drill!”

(4)With the message burned into his mind, First Mate Lovett all but ran up the ladder to the bridge.

(5) “Pearl harbor,” He choked out, “It’s been attacked!”

(6) Turning away from the ship’s compass, Captain Steele Looked at Lovett with narrowed eyes but made no reply.

(7) “Should we change course, Skipper?” Lovett blurted.

(8) Steel looked back at the ship’s compass but still had nothing to say.

(9) Lovett was beginning to feel frantic.

(10) In measured tones he said, “this message said, “this is no drill.” Should we still make for Kodiak?”

Look for missing commas in the passage. After which of thes words should a comma be added?

A. Sentence 6, "Steele"
B. Sentence 2, "Hilo"
C. Sentence 4, "Lovett"
D. Sentence 8, "but"

I think the answer is "D" Sentence 8.

A. Sentence 6, "Steele" No

B. Sentence 2, "Hilo" YES
C. Sentence 4, "Lovett" No
D. Sentence 8, "but" No

Do you need some good sources by which to study comma uses?
http://grammar.ccc.commnet.edu/grammar/commas.htm

Thanks and thank you for the link.

You are correct! The missing comma should be added in Sentence 8, after the word "but". Commas are used to separate two independent clauses that are connected by a coordinating conjunction (such as "and", "but", "or"). In this case, the comma is needed to separate the two independent clauses: "Steel looked back at the ship’s compass" and "still had nothing to say." The correct answer is D.