Question

lagoons are wetlands that form in the mouths of rivers along ocean coastlines. many trees fail in estuaries, but mangroves are an exception. mangroves are common in tropical estuaries, especially the everglades of southern florida. they thrive in the everglades because they tolerate much greater salinity levels than other plants do. they also have prop roots that support their weight in the everglades’ soil, which is wet and spongy, and often is covered in water. while the adaptations of mangroves are ideal for the everglades, they are less useful for other tropical regions, such as tropical rain forests—they can survive in those regions, but are less common there. the evidence in the passage most strongly supports which of these explanations of the range of mangroves?
a. mangroves depend on relatively warm temperatures.
b. mangroves depend on water of relatively high salinity.
c. other trees outcompete mangroves in low - salinity environments.
d. other trees outcompete mangroves in high - salinity environments.

Explanation:

The passage states mangroves are common in tropical estuaries (like Everglades) but less so in other tropical regions. Option B says mangroves depend on relatively high - salinity water. The Everglades has brackish (some salinity) water, and mangroves' adaptation to salinity (they can tolerate it, and other plants can't) explains their range—common in estuaries with salinity, less in regions without that salinity. Option A: The passage doesn't emphasize temperature as a limiting factor for their range in other tropical regions. Option C: If they thrived in low - salinity, they'd be more common in other tropical regions, which they aren't. Option D: The passage implies they do well in moderate - high salinity, not high - salinity environments (Everglades is brackish, not extremely high salinity). So B is supported.

Answer:

B. Mangroves depend on water of relatively high salinity