Answer:
I don't really know this one sorry
Explanation:
The speed of a wave is given by :
......(1)
(i) Here, the wavelength of a sound wave in air reduces by a factor of 3. Equation (1) becomes :

Wavelength and frequency are inversely proportional to each other. So, if wavelength of a sound wave in air reduces by a factor of 3, then the frequency will increases by a factor of 3.
(ii) It remains the same.
Answer:
3.75 hours
Explanation:
By 
where v is the velocity (or speed in this case)
d is the distance travelled
t is the time taken

Therefore it takes 3.75 hours for the bus to travel 150 km and 40 km/hr.
The first one is C. Hope this helps!! If you need anymore help just message me and I will try to get back to you quickly and help in any way i can!