Correct Answer - A
We have,
`a = "log"_(24) 12, b= "log"_(36)24 " and " c = "log"_(48) 36`
`rArr abc = "log"_(48) 12 " and " bc = "log"_(48)24`
`rArr abc - 2bc = "log"_(48) 12 -2"log"_(48) 24`
`rArr abc -2bc = "log"_(48) 12 - "log"_(48) 24^(2)`
`rArr abc - 2bc = "log"_(48) ((12)/(24^(2))) = "log"_(48)((1)/(48)) = -"log"_(48) = -1`
`rArr abc = 2bc-1`