Physics
The sky appears blue because

It is actually blue
In white light, the blue component dominates
The atmosphere scatters blue colour more than the others
All colours interfere to produce blue

ANSWER DOWNLOAD EXAMIANS APP

Physics
A balloon filled with hydrogen will

Reach a particular height and start coming down
Burst after reaching some height
Reach a particular height and remain floating
Continue going upwards uninterrupted

ANSWER DOWNLOAD EXAMIANS APP