The correct answer is C. streams.

A stream is a sequence of characters that can be read or written. In C++, streams are used to perform standard input and output operations. The standard input stream is called stdin, and the standard output stream is called stdout.

Characters are individual letters, numbers, and symbols. Sequences are a series of characters. Tests are used to check the condition of a variable or expression.

Here is an example of how to use a stream in C++:

“`c++

include

int main() {
std::cout << “Hello, world!”;
return 0;
}
“`

In this example, the std::cout object is a stream that is used to write output to the standard output stream. The << operator is used to write a value to a stream. In this case, the value "Hello, world!" is written to the standard output stream.

Streams are a powerful tool that can be used to perform a variety of input and output operations in C++.