Physics
In a railway track, two rails are joined end to end with a gap in between them because

Accidents due to contraction in winter can be avoided
Air-gaps are necessary for bearing the weight of running train
Accidents due to expansion in summer can be avoided
Steel can be saved

ANSWER DOWNLOAD EXAMIANS APP

Physics
Thermohaline circulation is mainly due to

Warm water being added to the ocean due to industial waste
Cold, dense ocean water sinking and warmer water replacing it
Winds causing circulation of ocean water
Warmer, less dense water sinking in the ocean and cold water replacing it

ANSWER DOWNLOAD EXAMIANS APP