ENGINEERING Write the word or phrase from the list that completes the sentence correctly. A(n) _____ is a sign indicating a passive railroad crossing. active railroad crossing, controlled intersection, crossbuck, delayed green light, fresh green light, gap, intersection, joining traffic, passive railroad crossing, point of no return, protected left turn, right of way, roundabout, safety stop, stale green light, uncontrolled intersection, unprotected left turn. ENGINEERING Consider the two-dimensional flow u = -Ax, υ = Ay, where A is a constant. Evaluate the circulation Γ around the rectangular closed curve defined by (x, y) = (1, 1), (4, 1), (4, 3), and (1, 3). Interpret your result, especially vis-ã -vis the velocity potential.