Question

1. what is the best way to combine sentences 21 and 22?

sucking up carbon dioxide and producing large amounts of oxygen are how this seagrass is like the rain forest.
this seagrass is like the rain forest that sucks up carbon dioxide that produces large amounts of oxygen.
although this seagrass sucks up carbon dioxide and produces large amounts of oxygen, the seagrass is like the rain forest.
like the rain forest, this seagrass sucks up carbon dioxide and produces large amounts of oxygen.

Explanation:

To determine the best way to combine the sentences, we analyze each option:

• The first option has an awkward structure ("are how this seagrass is like...").
• The second option has incorrect relative clause usage (two "that" clauses in a confusing way).
• The third option uses "although" incorrectly, as there's no contrast between the seagrass sucking carbon dioxide/producing oxygen and being like the rainforest.
• The fourth option ("Like the rain forest, this seagrass sucks up carbon dioxide and produces large amounts of oxygen.") clearly and concisely shows the similarity between the seagrass and the rainforest in terms of their functions (sucking CO₂ and producing O₂) with a proper structure.

Answer:

D. Like the rain forest, this seagrass sucks up carbon dioxide and produces large amounts of oxygen.