Answer:
The answer is: c. Adding external CSS is a good practice for various reasons, including code organization.
Explanation:
External CSS improves maintainability in code.
Internal CSS has precedence over external CSS, it means that internal will overwrite external CSS, but abuse of internal CSS often makes hard to maintain HTML code on a large website.
Furthermore, it is much easier to modify one CSS(external) file that can impact multiple web pages than go into every HTML page and modify your styles per page. Many sites have hundred or more pages, go through each one wouldn't be productive.
Let me re-write the proposition:
p↔q⊕(¬p↔¬r)∧¬q.
Generally, the number of rows in a truth table depends on the number of Variables. Here we have 3 Variables: p,q and r. Each of them can have either the value of 1 or 0, which gives us 2*2*2 possibilities, or 2³, that is 8 possibilities and 8 rows:
p=0, q=0, r=0
p=0, q=0, r=1
p=0, q=1, r=0
p=0, q=1, r=1
p=1, q=0, r=0
p=1, q=0, r=1
p=1, q=1, r=0
p=1, q=1, r=1