Final answer:
In an old version of holiday lights, when one bulb burnt out, it caused all the other bulbs to go out. In newer versions, the remaining bulbs remain unaffected when one bulb burns out.
Step-by-step explanation:
In an old version of holiday lights, when one bulb burnt out, it broke the electrical connection, causing all the other bulbs to go out. So, the answer is A) They all went out.
However, in newer versions of holiday lights, when one bulb burns out, it short circuits and acts like a closed switch. So, the remaining bulbs in the string remain unaffected. The answer to the second part of the question is C) They remained unaffected.