The correct answer is: A. can have only positive values.
An unsigned double type of data can have only positive values. It is a 64-bit data type that can store a value between 0 and 2^63-1.
Option B is incorrect because unsigned double type of data does exist.
Option C is incorrect because unsigned double type of data is not always less than 1010. It can store a value between 0 and 2^63-1, which is much larger than 1010.
Option D is incorrect because unsigned double type of data can have positive values.
Option E is the correct answer because it is the only option that is not contradicted by the other options.