1. ans - d.
The candle will extinguish if the CO₂ is formed in the reaction. CO₂ will be formed in tube I and IV only. So It will not be extinguished in tubes II and III.
2. ans - a
If object is located at infinity, then an inverted image will be formed at the focus. So if you remove the screen and see, you will see an inverted tree.
3. ans - b.
Even if the lower portion is covered, the upper portion will still act as a lens and form the complete image. But the clarity of the image will be less. So we can say it fades.
4. ans - b
When object is placed between focus and the converging lens, virtual,erect and magnified image is formed on the same side of the lens.