SAT English Practice Question

A researcher studying the mating habits of the common octopus (Octopus vulgaris) was surprised to find that, rather than selecting a mate based on visual cues, male octopuses seemed to favor a female based on her sense of smell. The research team hypothesized that, during their mating rituals, the male octopuses secrete a chemical pheromone that the females can smell and that this pheromone influences the female’s choice of mate. What would be the best way to revise the underlined portion of the sentence to improve the clarity of the passage?

1. A.replace "that" with "which"
2. B.replace "that" with "who"
3. C.remove the phrase "that the females can smell"
4. D.change "that this pheromone influences the female’s choice of mate" to "which influences the females’ choice of mate"