In the following code fragment, which is the calling object for the less-than operator?string s1, s2;if( s1 < s2 )a.s1b.s2c.<d.None.

Understanding the Code Fragment

In the provided code fragment, we need to identify which string object is the calling object for the less-than operator (<).

1. Code Understanding: The expression if (s1 < s2) means that s1 is being compared to s2 using the less-than operator.

2. Calling Object: In C++, for the expression a < b, the object a is considered the calling object, and the operator function will be called on this object.

Analysis of the Options

1. Option a. s1: This represents the first string object on the left of the less-than operator.
2. Option b. s2: This represents the second string object on the right side of the operator.
3. Option c. <: This is the operator itself, not an object.
4. Option d. None: Indicates no suitable option.

Conclusion

In this case, the calling object is s1, as it is the object that invokes the operator function to compare itself with s2.

Final Answer

The calling object for the less-than operator is a. s1.