The correct answer is: D. occupies only the size it needs and not the full block
A file in HDFS that is smaller than a single block size will occupy only the size it needs and not the full block. This is because HDFS stores files in blocks, and each block is a fixed size. If a file is smaller than a block, it will only occupy the space that it needs.
Option A is incorrect because a file in HDFS can be stored even if it is smaller than a single block size.
Option B is incorrect because a file in HDFS will only occupy the space that it needs, even if it is smaller than a single block size.
Option C is incorrect because a file in HDFS cannot span over multiple blocks if it is smaller than a single block size.