Answer: Dark matter.
Explanation: Hope it helps :)
The train is moving at 50 m/s and Emma is walking down the aisle with 1 m/s speed in the same direction of train. The relative velocity of Emma with respect to other passengers pf the train would be 1 m/s. This is because, the train is not moving relative to them and only emma is moving at 1 m/s. If a person observes from outside, Emma would have (50 +1) m/s = 51 m/s velocity.
relative velocity when two objects are moving in same direction as oberved from outside observer:

relative velocity when two objects are moving in the opposite directionas oberved from outside observer:

Answer: Non metal.
Explanation: Carbon has 4 electrons in it’s valence shell which makes it a metalloid but commonly it is considered as a non metal.
Answer:It is an Endothermic reaction
Explanation:
Exothermic reaction
An exothermic reaction is one that releases energy in the form of heat or light.
Endothermic reaction
An endothermic reaction is one that absorbs energy in the form of heat or light.
Answer:
C
Explanation:
The sun has rotated causing the shadow to reflect.