To answer this question, the user needs to have knowledge of programming concepts, specifically the concept of variable scope.

The scope of a variable refers to the accessibility or visibility of the variable within a program. It determines where and how the variable can be accessed and used.

Now, let's go through each option and explain why it is right or wrong:

A. the length of the variable: This option is incorrect. The scope of a variable is not related to its length. The length of a variable may refer to the number of characters or bytes used to store its value, but that is not the same as its scope.

B. the name of the variable: This option is incorrect. The scope of a variable is not determined by its name. While the name of a variable is important for identifying and referencing it, it does not define its scope.

C. the accessibility of the variable: This option is correct. The scope of a variable refers to its accessibility within a program. It determines where and how the variable can be accessed and used. The accessibility of a variable can be influenced by factors such as its declaration location and the programming language being used.

D. the datatype of the variable: This option is incorrect. The scope of a variable is not related to its data type. The data type of a variable determines the type of values it can store, but it does not define its scope.

E. the lifetime of the variable: This option is incorrect. The scope of a variable and its lifetime are related concepts but not the same. The lifetime of a variable refers to the period during which the variable exists in memory, whereas the scope refers to where and how the variable can be accessed within a program.

The Answer is: C. the accessibility of the variable.