A.
The maxWidth, the third parameter of fillText() method, is optional.
B.
The fillText() method can draw a text string in the canvas.
C.
When arc() method draws an arc, its last parameter is true or fasle, that is, whether it is clockwise or not, and it cannot be omitted.
D.
The clearRect(width, height, left,top) method is used to clear all the contents in the rectangular area with width=width and height=height and the top left corner at (left, top).