The correct options are
A n is an odd numbers
C sometimes a perfect square
Letx=a(a+1)(a+2)(a+3)Nowwhetheraisevenorodd,thefourconsecutivenumber′sproductcontain2,3,4asfactors.∴xisdivisibleby2×3×4=24−−−−(1)OptionA⟶Fourconsecutivenumberscontaintwoevennumbers.Thereforeproductiseven.∴x+1shouldbeodd.OptionAiscorrect.OptionB⟶xisdivisibleby24(from1)Nowthereexistsnoprimeoftheform24p+1wherepisanaturalnumber.e.g.29=24×1+531=24×1+737=24×1+13Withincreasingcountthesecondtermincreasesbecausedifferencebetweenprimesincreasewithhighercount.Thereforex+1=nisnotaprimeunderthegivencondition.Foraexpandednumbertobesquare,thefirstandlasttermshouldbesquarenumber.OptionC⟶x=a(a+1)(a+2)(a+3)whenaisevena=2p∴x=2p(2a+1)(2a+2)(2a+3)=4p(2p+1)(p+1)(2p+3)Theproductis4×1×1×3=12Ifweadd1thenlasttermoftheproductis13whichisnotasquarenumber.Sox+1=nisnotasquarenumberwhenaiseven.(2)Whenaisodd−x=(2p+1)(2p+2)(2p+3)(2p+4)Thelasttermoftheproductis1×2×3×4=24.24+1=25isasquareterm.∴n=x+1isasquarenumberwhenaisodd.∴OptionCiscorrectwhenaisodd.OptionD⟶ObviouslyoptionDisnotcorrect.