Nhận biết (M1)

Phosphine (PH3) — on Earth a gas arising almost only from biological sources — was apparently detected in the cloud deck of Venus in 2020, and the finding stays controversial for all the prospect of independent confirmation, partly because Venus is taken to be uninhabitable. Weighing its plausibility, William Bains et al. modelled abiotic routes to PH3 — geochemical, atmospheric, photochemical — and none accounts for the levels observed. Venusian PH3, if real, would point to gaps in the present consensus on the chemistry of Venus.

Which choice best describes the overall structure of the text?

• A.

  It sets the levels of one gas on Venus against those on Earth, sketches the chemistry accounting for the difference, and then takes up some practical difficulties in studying the gas on Venus more closely.

• B.

  It explains why the consensus view of one gas in the atmosphere of Venus has lately grown controversial, expands on a team’s grounds for doubting that consensus, and then suggests that further observation will probably be needed to settle the matter.

• C.

  It outlines recent attempts to confirm that a gas is present in the atmosphere of Venus, sums up a team’s assessment of where those attempts fell short methodologically, and then explains why the team doubts the gas will be detected.

• D.

  It sets out a consensus long held about a gas in the atmosphere of Venus, describes an experiment that overturned it, and then predicts the gas will shortly be detected directly.