The following
statement about canvas is correct ()
选项：

A:MaxWidth, the
third parameter of fillText (), is optional
B:The fillText ()
method can draw a string in the canvas
C:arc()drawing
a circle is true or whether fasle is clockwise cannot be omitted
D:clearRect(width,height,left,top) clears all
contents in the rectangular area with width, height and the vertex of
the upper left corner at (left, top).