Read the passage below and fill in the blank with the correct past-tense form of the verb in parentheses to maintain consistent verb tense throughout the paragraph.
Answer:In the early twentieth century, acoustic engineers began studying how sound waves propagate through underwater environments. They discovered that sound travels significantly farther in water than in air, enabling marine mammals to communicate across vast oceanic distances. When researchers first deployed submerged hydrophones during wartime tests in the 1940s, they 【heard】 (hear) a complex array of low-frequency whale songs that transformed scientific understanding of marine biology.
Answer
The correct verb form to complete the passage is 'heard'.
The simple past tense verb 'heard' maintains consistent temporal alignment with the surrounding past-tense verbs ('began', 'discovered', 'deployed', 'transformed') and the explicit past-time frame indicator ('in the 1940s').
Step-by-Step Solution
Key Concept
Verb Tense and Consistency