Concept:The correct word must be opposite in meaning to “insignificant” and fit the sentence logically.Explanation:"Insignificant" means unimportant or not worth attention.The Registrar considers the matter unimportant, but his deputy sees it as very important.The most nearly opposite word for "insignificant" among the options is "crucial," which means of great importance."Minute" and "marvellous" are not correct opposites in this context, and "compulsory" means required, not important.Answer:B. crucial