What is the output datatype when using String.Format("{0} is {1}", VarName1, VarName2) to convert values of objects into strings?

When using the String.Format method with the format string "{0} is {1}" and passing in variables like VarName1 and VarName2, the output datatype is indeed a String. The String.Format method is designed to create a new formatted string by substituting placeholders (such as {0} and {1}) with the corresponding values provided as arguments.

This method takes each variable and converts it to its string representation, effectively concatenating them into a single output string based on the specified format. The final result of the String.Format call will always be a string, regardless of the types of VarName1 and VarName2. Thus, the correct answer reflects the nature of the output produced by this string formatting function.