Questions 3-4 refer to the following passage

Which of the following, if true, would most weaken the author’s conclusion about the hydrogen sulfide theory?

a. The oceanic sediment is geologically inactive.

b. Changes in the chemical composition of oceanic sediment have rendered the Permian period indistinguishable from earlier periods.

c. The oceanic sediments of the Permian period contain unusually high levels of carbon.

d. The oceanic sediments contain many chemicals more toxic than simple hydrogen sulfide.

e. The oceanic sediments can mask large populations of other types of bacteria.

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(5) Theorists are divided about the cause of the Permian mass extinctions. Some hypothesize that the impact of a massive asteroid caused a Line sudden disappearance of species. However, a look at the carbon-isotope record suggests that existing plant communities were struck down and re-formed several times. To produce such a pattern would require a succession of asteroid. strikes thousands of years apart. Other theo- (10) rists have proposed that volcanic explosions raised the CO₂ levels, leading to intense global warming. One problem with this theory is that it cannot explain the massive marine extinctions at the end of the Permian period. A new theory (15) posits that rising concentrations of toxic hydro- gen sulfide in the world's oceans plus gradual oxygen depletions in the surface waters caused the extinctions. Fortunately, this theory is test- able. If true, oceanic sediments from the (20) Permian period would yield chemical evidence of a rise in hydrogen sulfide-consuming bacteria.