In Death Valley National Park's Racetrack Playa, a flat, dry lakebed, are 162 rocks-some weighing less than a pound but others almost 700 pounds-that move periodically from place to place, seemingly of their own volition Racetrack-like trails in the __ mysterious migration. 16 Which choice completes the text so that it conforms to the conventions of Standard English? A playas sediment mark the rock's B playa's sediment mark the rocks C playa's sediment mark the rocks' D playas' sediment mark the rocks'

## Step 1<br />The problem is a multiple-choice question that tests your understanding of possessive forms in English grammar. The sentence in question is about a flat, dry lakebed in Death Valley National Park, where rocks move periodically. The sentence is incomplete and needs to be completed in a way that conforms to the conventions of Standard English.<br /><br />## Step 2<br />The options provided are:<br />A. playas sediment mark the rock's<br />B. playa's sediment mark the rocks<br />C. playa's sediment mark the rocks'<br />D. playas' sediment mark the rocks'<br /><br />## Step 3<br />The correct answer is B. "playa's sediment mark the rocks". This is because the sentence is talking about a single 'playa', which is a Spanish word for a flat, dry lakebed. Therefore, the possessive form should be 'playa's', not 'playas' or 'playas''.<br /><br />## Step 4<br />The sentence is also talking about multiple rocks, so the plural form 'rocks' should be used, not 'rock's' or 'rocks''.