15. What is the correct piecewise parametrization of a path C created by starting from C₁ of equation y = x + 3 from x = 0 to x = 4, then C₂ with an equation y = x² from y = 7 to the origin and a vertical line C3 that connects the two previous curves head to tail? A. r(t)=4-t 0≤t≤4 4≤t≤4+√7 4+√7≤t≤7+√7 0 t+4+√7 t + 3 t 0≤t≤4 4≤t≤4+√7 (4-t)² 0 t+4+√7 4+√7≤t≤7+√7 B. r(t)=4-t t+3 4-t² 't D. r(t) = t 0 t t + 3 C. r(t) = 4+√7-t (4+√7-t)² 4+√7-0 0 t-4-√7 t + 3 0≤t≤4 t² 0≤t≤√7 t 0 ≤t≤3 0≤t≤4 4≤t≤4+√7 4+√7 ≤ t ≤7+√7 O