Step 1, compare the size of A with that of B and C, and output the value of A when A is greater than B and C;
When A cannot be greater than B and C at the same time, proceed to step 2;
Step 2, because A is not the maximum, compare the sizes of B and C..
When b > c, output b; When b < c, c is output.
To sum up, the blank judgment box should be filled in: a > b? And then what? a>c？
So choose: D.