1.Present participle as a noun: "Engaging in regular physical activity" uses the present participle "engaging" as a noun, demonstrating advanced grammar usage.
2.Correlative conjunction: "not only... but also" is used to connect two related ideas, enhancing the complexity and coherence of the sentence.
3.Present simple tense: "Regular exercise strengthens the immune system" uses the present simple tense to state a general fact, showcasing the ability to use different tenses appropriately.
4.Adverbial phrase: "significantly reduces the risk of chronic diseases" uses an adverbial phrase to modify the verb "reduces," adding depth and precision to the sentence.