It probably is the actual answer.
The category of galaxy which does not have a distinctive shape is D. an irregular galaxy.
A spiral galaxy has a spiral shape, an elliptical galaxy has an elliptical shape, and a barred-spiral galaxy has a barred-spiral shape. The only galaxy type which does not have a constant shape is an irregular galaxy.
Atomic mass = number of protons + number of neutrons = 4+5 = 9 amu
I would say 150 joules, i don't know if its right though check
Answer:
Explanation:
The relationship between angle and wavelength for maxima and minima in Young's double slit experiment is given by
For constructive interference

For Destructive interference

where 

m=order of maxima and minima
for second order maxima i.e. 
For smallest separation taking 


