A.
var g = context.createLinearGradient(0,0,0,700); g.addColorStop(2,'rgb(255,0,0)');
B.
var g = context.createLinearGradient(0,0,700,0); g.addColorStop(0.5,'rgb(255,0,0)');
C.
var g = context.createLinearGradient(0,0,700,0); g.addcolorstop(0.5,'rgb(255,0,0)');
D.
var g = context.createRadialGradient(400,200,0,400,200,40); g.AddColorStop(0,'rgb(255,0,0)');