What method call would we use to determine if a char ch is a capital letter?

Which of the following are valid method calls? Select all valid method calls given:

 char c = 'c'; String s = "s"; 

Select one or more:

a.

Character.isDigit(c);

b.

c.toLowerCase();

c.

"s".length();

d.

c.length();

e.

Character.toUpperCase(c);

f.

'c'.length();

g.

s.isDigit();

h.

s.toUpperCase();

i.

c.isDigit();