Using self-reference very often creates trouble: an inherent
inconsistency or leads to answers which are hard to discover.
Analyze the test below and answer the following:

Is this test inconsistent? If not, give all answers which are
correct. A sample incorrect answer could be (1a 2b 3b 4b 5a).
This is incorrect, since it has two questions with answer 'a',
while the first part '1a' says that there are none.

1. How many questions on this test have the answer 'a'?
a. 0
b. 1
c. 2
d. 3
e. 4

2. How many questions on this test have the answer 'b'?
a. 0
b. 1
c. 2
d. 3
e. 4

3. How many questions on this test have the answer 'c'?
a. 0
b. 1
c. 2
d. 3
e. 4

4. How many questions on this test have the answer 'd'?
a. 0
b. 1
c. 2
d. 3
e. 4

5. How many questions on this test have the answer 'e'?
a. 0
b. 1
c. 2
d. 3
e. 4