AB or BC. Polynomials. I used this to introduce this to my AB AP Calculus students while I was out for the birth of my second child (first daughter!). It introduces the FTC as difference of the evaluations of the general antiderivative at the upper and lower bounds and also includes a connection to simple bounded area. The students had knowledge of Riemann sums as approximations and the limit definition of area as well as antiderivatives and indefinite integration with simple functions the week before.
I like this circuit a lot as an introductory challenge and it is what I call a 'mobius'. The circuit finishes early (in this case three cells early) and the remaining cells create their own circuit (lettered instead of numbered). The intent of this style is to help prevent the students from using process of elimination to complete the last few cells which tend to be more difficult problems.