https://foxoyo.com/mcq/1391/a-sentencea-part-of-the-sentence-is-underlined-four-alternatives-are-given-to-the-underlined-part-which-will-improve-the-sentence-choose-the-correct-alternative-and-click-the-button-corresponding-to-it-in-case-no-improvement-is-needed-click-the-button-corresponding-to-no-improvement-mankind-does-not-know-this