Consider the following method. An 11-line code segment reads as follows. Line 1: public static boolean mystery, open parenthesis, String str, close parenthesis.
Line 2: open brace.
Line 3: String temp equals, open double quote, close double quote, semicolon.
Line 4: blank.
Line 5: for, open parenthesis, int k equals str, dot, length, open parenthesis, close parenthesis, semicolon, k greater than 0, semicolon, k minus, minus, close parenthesis.
Line 6: open brace.
Line 7: temp equals temp plus str, dot, substring, open parenthesis, k minus 1 comma k, close parenthesis, semicolon.
Line 8: close brace.
Line 9: blank.
Line 10: return temp, dot, equals, open parenthesis, str, close parenthesis, semicolon.
Line 11: close brace.

Required:
What calls to mystery will return true?