Answer:
C is the best answer because we all know that clock is part of our daily lives but we don't know the about its background
Yes. Copper, mercury, and tin are all used to fill in cavities.
Its true hopefully this helps you.
Answer:

Explanation:
It is given that,
The number of lines per unit length, N = 900 slits per cm
Distance between the formed pattern and the grating, l = 2.3 m
n the first-order spectrum, maxima for two different wavelengths are separated on the screen by 2.98 mm, 
Let d is the slit width of the grating,



For the first wavelength, the position of maxima is given by :

For the other wavelength, the position of maxima is given by :

So,



or

So, the difference between these wavelengths is 14.3 nm. Hence, this is the required solution.
10cm per beat, it would take 3 beats to travel 30cm x