Question

phytoplankton play a crucial role in the oceans uptake of carbon from the atmosphere. when alive, these tiny marine organisms absorb atmospheric carbon via photosynthesis. after they die, the phytoplankton sink to the seafloor, where the carbon in their cells gets stored in sediment, preventing it from cycling back into the atmosphere. 23 mark for review which choice completes the text with the most logical transition? a specifically, b by contrast, c nevertheless, d then,

Explanation:

The first sentence describes phytoplankton absorbing carbon when alive. The second sentence shows what happens after they die (a sequential event). "Then" indicates a sequence of events. "Specifically" is for giving details, "By contrast" for showing differences (no contrast here as both actions contribute to carbon uptake), and "Nevertheless" for a contrast/opposition (not the case here).

Answer:

D. Then,