In the question below, a paragraph is split into several parts. Examine each part for grammatical accuracy and select the option that correctly identifies which parts are grammatically correct or incorrect.

(A) This year’s increased rainfall have caused frequent waterlogging across the city. (B) If the drainage network is maintained before the heaviest spells, (C) neighborhoods will be spared repeated flooding. Farmers report that reservoirs have filled early, helping irrigation (D) but also raising the risk of pests. While forecasts predict continued showers, but officials advise residents to avoid low-lying underpasses. (E) Because timely alerts have been issued this year, many commuters have started leaving home earlier to avoid gridlock.

The correct option is A and D are incorrect.

Let's analyze each sentence part to identify the grammatical errors:

Part (A): "This year’s increased rainfall have caused frequent waterlogging across the city."
- Analysis: The subject of the clause is "rainfall" (or "increased rainfall"), which is an uncountable singular noun. Therefore, it requires the singular verb "has caused" instead of the plural verb "have caused".
- Correction: "This year’s increased rainfall has caused frequent waterlogging across the city."
- Status: Incorrect.

Part (B): "If the drainage network is maintained before the heaviest spells,"
- Analysis: This is a grammatically correct conditional clause using standard subject-verb agreement and prepositional usage.
- Status: Correct.

Part (C): "neighborhoods will be spared repeated flooding. Farmers report that reservoirs have filled early, helping irrigation"
- Analysis: This sentence is grammatically sound. The future tense "will be spared" properly pairs with the conditional clause in Part (B), and the subsequent sentence maintains correct tense and structure.
- Status: Correct.

Part (D): "but also raising the risk of pests. While forecasts predict continued showers, but officials advise residents to avoid low-lying underpasses."
- Analysis: This part contains a redundant conjunction error. The sentence starts with the subordinating conjunction "While", which establishes a contrast. Adding the coordinating conjunction "but" in the main clause creates a double conjunction error.
- Correction: "While forecasts predict continued showers, officials advise residents to avoid low-lying underpasses." (Remove "but").
- Status: Incorrect.

Part (E): "Because timely alerts have been issued this year, many commuters have started leaving home earlier to avoid gridlock."
- Analysis: The subordinating clause introduced by "Because" is correctly followed by the main clause without unnecessary conjunctions, and all verb tenses match appropriately.
- Status: Correct.

Conclusion:
Parts A and D contain grammatical errors, while parts B, C, and E are correct. Hence, the option identifying A and D are incorrect is the correct choice.