Explanation:(in order the of pathway of food down the digestive tract)
food first passes through the small intestine ( duodenum, jejunum, ileum) and then enters the large intestine ( caecum, colon, rectum).
any function of sin cos and other trigonometric ratios is taken as 1.for ex. in ur qstion dimensions for [dt] and [by] can be equated as 1.so dimension of d will be t^-1 and for b will be l^-1. so [d/b ] is equal to t^-1/l^-1=l/t