In this question, the subject "balanced diet and regular exercise" is plural, so the plural form "are" (choice D) is the appropriate option. Choice A (is) is the singular form of the verb, choice B (has been) opts for the singular form in the present perfect tense, and choice C (were) opts for the past simple tense.

This question is testing subject-verb agreement with the subject "algae and bacteria." The correct verb form is "undergo" (choice B), as it is the plural form of the verb to agree with the plural subject. Choice A (undergoes) is the singular form, choice C (was undergoing) changes the tense to the past continuous, and choice D (had undergone) opts for the past perfect tense.

In this question, the subject is "climate change and the resulting alterations in weather patterns." The correct verb form is "pose" (choice A), as it is the plural form of the verb to agree with the plural subject. Choice B (poses) is the singular form, choices C (has posed) and D (had posed) both opt for different past perfect tenses.

In this question, the subject "advancements" is plural, so the plural form "have made" (choice B) is the appropriate option. Choice A (has made) is the singular form of the verb, choice C (made) opts for the past simple tense, and choice D (had made) opts for the past perfect tense.

The subject "array of online resources and tools" is singular because "array" is the main subject, so choice A (presents) is the appropriate choice. Choice B (present) is the plural form, choice C (presented) changes the tense to the past, and choice D (will present) opts for the future tense, less appropriate than the present simple tense.