/* missing precondition */ public String getChar(String str, int n) {

return str. substring(n, n 1); }

Write down the most appropriate precondition for the method so that it does not throw an exception.

An appropriate precondition is:

0 <= n && n <= str.length() - 1

Explanation:

Required:

Write down an appropriate pre-condition for the program

From the question, we understand that the method accepts two parameters:

str -> A string value

n -> An integer value which represents the index of character to return from the string str

It should be noted that:

n must be within the range of 0 and str.length()-1

Take for instance:

str = "ABCDE";

n must be within the range 0 to 4 (inclusive) in order not to raise an exception. This is so because the string index starts at 0 and stops at 1 less than the length of the string.

Hence, the precondition can be written as:

0 <= n && n <= str.length() - 1

Which means: n = 0 to length - 1

answers

a. nitrogen (n)

d. oxygen (o)

hope it