In order to use Green's Theorem, certain conditions must be met. Which of the following conditions must be true? Select all that apply. O F must be in the direction of C. O F = Vf = U R is on the right as we move around the curve C. O R is on the left as we move around the curve C. O F is a smooth field on an open region containing C and R. O C is a piecewise smooth simple closed curve that is the boundary of R.