Skipped question is graded as correct when the real correct answer is "False"

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Set the answer key for a question to the word False
2. Take the test and skip this question
3. Grade the test. This skipped question will be counted as correct.

What is the expected output? What do you see instead?
The expected output is a score of zero on the question. The actual output is a 
score equal to the point value of the question.

What version of the product are you using? On what operating system?
Version 28

Please provide any additional information below.
The answer string "False" is evaluated as the Boolean FALSE in the submissions 
sheet. This is matching a blank entry during the grading process.

Original issue reported on code.google.com by jlb...@gmail.com on 16 Jul 2015 at 2:10

[GoogleCodeExporter]

Found a related issue: If the student enters the string "1/4" as an answer, the 
submissions sheet interprets this as a date and enters 1/4/2015 as the answer.

Original comment by jlb...@gmail.com on 16 Jul 2015 at 6:34

[GoogleCodeExporter]

Found another related issue: If the student enters a ratio, such as 15:4, as 
the answer to a question, the submissions sheet interprets it as a time and 
enters 15:04 as the answer.

Original comment by jlb...@gmail.com on 16 Jul 2015 at 9:25