In each of the questions given below, four sentences have been given. Out of four sentences, one sentence has an error. Find out which of the following sentence has an error. If all the given sentences are error-free then choose option ‘ All are correct’ as your answer choice.

Select the sentence that contains a grammatical error, or select 'All are correct' if every sentence is correct:

The correct answer is: "The volunteers labored throughout the week to constructed a sturdy shelter."

Step-by-Step Explanation:

1. Identifying the Grammatical Error:
In the sentence "The volunteers labored throughout the week to constructed a sturdy shelter," there is a clear error in the use of the verb form following the preposition "to".
An infinitive phrase consists of the word "to" followed by the base form of a verb (bare infinitive). Therefore, the preposition "to" must be followed by "construct" instead of the past-tense form "constructed".

Correction:
"The volunteers labored throughout the week to construct a sturdy shelter."

2. Analyzing the Other Options:
• "Individuals with strong communication skills can effortlessly persuade others." — This sentence is grammatically correct. The modal verb "can" is properly paired with the base verb "persuade", and the adverb "effortlessly" correctly modifies the verb.
• "An ancient oak tree has recently turned into a popular gathering spot for neighborhood residents." — This sentence is grammatically correct. The present perfect tense ("has recently turned") is used properly with the singular subject "oak tree".
• "Whispering a quick plea to the heavens, she immersed her feet into the stream and crossed the river." — This sentence is grammatically correct. The introductory participial phrase ("Whispering...") correctly modifies the subject "she", and the past-tense verbs ("immersed", "crossed") maintain parallel structure.

Hence, the sentence containing the grammatical error is "The volunteers labored throughout the week to constructed a sturdy shelter."