Well, a pure substance Is something that isn't mixed with anything else. it is it's own thing, and a mixture can be separated by physical means, so it is A.
I only know P and V and P is pressure and V is volume
It can never be shorter than a component - magnitude of a vector is the square root of the sum of the components squared, and a square function never produces a negative number. However, it can be the same size as it's component, if that component is the only one.
C. Speed in a giving direction
Answer:
The distance between the slits is given by 1.3 ×
m
Given:

D = 4 m
y = 
m = 1
To find:
distance between slits, d = ?
Formula used:
y = 
y = distance of first bright band from central maxima
D = distance between screen and source
d = distance between slits
= wavelength
Solution:
distance of first bright band from central maxima is given by,
y = 
y = distance of first bright band from central maxima
D = distance between screen and source
d = distance between slits
= wavelength
Thus,
d = 
d = 
d = 1.28 × 
d = 1.3 ×
m
The distance between the slits is given by 1.3 ×
m