What operator is used to assign a value to a declared variable?

The operator that is used to assign a value to a declared variable in C is the equals sign, also known as the assignment operator. This operator works by taking the value on the right side and assigning it to the variable on the left side. For instance, if you have a variable declared like int x;, you would use the assignment operator to set its value by writing x = 5;. This statement assigns the value 5 to the variable x.

Other options do not serve the purpose of assignment. The plus and minus operators are used for arithmetic operations, such as addition and subtraction, whereas colons have specific syntactical uses in C but do not facilitate variable assignment. Understanding the correct use of the assignment operator is fundamental in C programming, as it enables the modification of variable values throughout the program's execution.