Which sentence correctly uses a comma to separate coordinate adjectives?
my father bought a new, wood desk for his office.
a red, rusty gate blocked the opening of the trail.
a cool, chocolate milkshake tastes great on a hot day.
my sister drives a bright, pink minivan to work every day.
i put a?

The correct answer is B, "A red, rusty gate blocked the opening of the trail."

Coordinate adjectives are in a row and both separately modify the subject. You can rearrange the order of the adjectives without confusion. For example, I could say, "A rusty, red gate blocked the opening of the trail," without changing the meaning or fluency of the sentence. In the other sentences, it is impossible to change the order of the adjectives and still have a coherent, fluid sentence.

the maximum speed limit is 55 mph on a two-lane undivided highway and for vehicles towing trailers.

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