To answer this question, let's go through each option to understand why it is correct or incorrect:
Option A) all blanks - This option is incorrect because the initial value of a variable in REXX is not all blanks. The initial value will be determined by the assignment or the default value of the data type.
Option B) NULL value - This option is incorrect because REXX does not have a specific NULL value. The initial value of a variable will be determined by the assignment or the default value of the data type.
Option C) name of the variable in the same (mixed) case as the name - This option is incorrect because the initial value of a variable in REXX is not based on the variable name itself. The initial value will be determined by the assignment or the default value of the data type.
Option D) name of the variable in uppercase - This option is correct because when defining a variable in REXX, the initial value will be the name of the variable in uppercase. This means that the variable will initially have the same value as its name, but in uppercase.
The correct answer is D) name of the variable in uppercase. This option is correct because the initial value of a variable in REXX is the name of the variable in uppercase.