IMO the answer is E.
So, the passage starts by giving some stats that "Many Americans do not take all the vacation time to which they are entitled", then it goes on the give reasons, as to Why is this happening. Then the auther gives his/her opinion, by saying "This is a mistake"; and then provides explanation as to Why he thinks this is a mistake.
Let`s start by eliminating the incorrect answer choices:
A: recommendation; it is not a recommendation. The author is not recommending this, it is already happening. Eliminated.
B: evidence; hmm this could be it but on gurther reading it says "evidence of the author’s claim". It is not an evidence of authors claim. Eliminated.
C: conclusion; it is not conculsion as analysed while reading, conclusion is different. Eliminated.
D: statement of a principle; it is not a principle further it is completely opposite from what author wants people to observe. Eliminated.
E: statement of a fact; this is as per our understanding and the author is definately expressing his/her opinion about this fact. Correct.