Question

research on chaenocephalus aceratus and other icefishes of the teleostei class has shown that their hearts are pale due to low levels of myoglobin expression, which was once thought to be related to their polar habitats. recently, researchers have found that some tropical teleost species (such as sphaeramia nematoptera) also have pale hearts, raising the possibility that myoglobin deficiency in teleosts could be______habitat.
which choice completes the text with the most logical and precise word or phrase?
a irrespective of
b mediated by
c predictive of
d obscured by

Explanation:

The text first mentions that icefishes (originally thought related to polar habitats) have pale hearts due to low myoglobin. Then it says some tropical teleosts also have pale hearts. This implies that myoglobin deficiency is not dependent on habitat. "Irrespective of" means regardless of. "Mediated by" (B) would imply habitat causes it (contradicts the new finding). "Predictive of" (C) would mean myoglobin deficiency shows habitat (opposite). "Obscured by" (D) is not relevant.

Answer:

A. irrespective of