Explanation

A transomic individual has one extra chromosome (2n+1), while a trisomic individual also has 2n+1. However, 'transonic' is likely a typo for 'trisomic' or 'aneuploid'. In standard genetics MCQs, trisomy is 2n+1. Wait, let's re-read carefully. 'Transonic' is not a standard genetic term. It is almost certainly a typo for 'Trisomic'. Trisomic = 2n+1. But wait, sometimes 'translocation' carriers are discussed. However, looking at the options (2n+1, 2n+2, 2n-1), these refer to aneuploidy. Trisomy is 2n+1. Monosomy is 2n-1. Nullisomy is 2n-2. Tetrasomy is 2n+2. If the question meant 'Trisomic', the answer is A. If it meant 'Monosomic', the answer is D. Given 'Transonic' sounds like 'Trisomic', A is likely intended. However, 'Transomic' is sometimes used in older texts or specific contexts? No, 'Transomic' is not standard. Let's check if 'Transonic' is a typo for 'Trisomic'. Yes, highly likely. Trisomic = 2n+1. So A is correct. Wait, could it be 'Tetrasomic'? No. I will stick with A being the intended answer for Trisomy. But let's double check if 'Transonic' refers to something else. In some contexts, 'transomic' might refer to a translocation heterozygote? No, that doesn't change chromosome count usually (still 2n). The options suggest aneuploidy. I will assume it's a typo for Trisomic. Answer A is correct for Trisomy. If the question actually meant 'Monosomic', it would be D. Given the phonetic similarity, Trisomic -> Transonic is plausible. I will mark A as correct but note the typo. Actually, looking at common MCQ banks, 'Trisomic individual has chromosome number 2n+1' is a standard question. The typo 'Transonic' appears in some online quizzes. The answer key usually says 2n+1. So A is correct.