D.
Electromagnetic waves are received and then vibrate a speaker which produces sound waves.
Explanation:
The telephone has a receiver-transducer component that can receive electromagnetic wave - radio waves spectrum- and transform them into electric energy. This electric energy is then transformed into sound energy by a speaker. This is how we're able to listen to a phone call.
The opposite happens when we speak on the phone. The sound energy is transformed into electric energy by a microphone – the reverse of a speaker. The transducer now changes the electric energy into electromagnetic waves that travel through space to the recipient in the phone conversation.
Answer:
The empirical formula of the compound is = 
The name of the compound is potassium bromate.
Explanation:
Mass of potassium = 4.628 g
Moles of potassium = 
Mass of bromine = 9.457 g
Moles of bromine = 
Mass of oxygen = 5.681 g
Moles of oxygen = 
For empirical formula of the compound, divide the least number of moles from all the moles of elements present in the compound:
Potassium :

Bromine;

Oxygen ;

The empirical formula of the compound is = 
The name of the compound is potassium bromate.
Answer:
The concentrations are :
![[HAsc^-]=0.000702 M](https://tex.z-dn.net/?f=%5BHAsc%5E-%5D%3D0.000702%20M)
![[Asc^{2-}]=5.92\times 10^{-8} M](https://tex.z-dn.net/?f=%5BAsc%5E%7B2-%7D%5D%3D5.92%5Ctimes%2010%5E%7B-8%7D%20M)
The pH of the solution is 3.15.
Explanation:

Initial
c 0 0
Equilibrium
c-x x x
![K_{a1}=\frac{[HAs^-][H^+]}{[H_2Asc]}](https://tex.z-dn.net/?f=K_%7Ba1%7D%3D%5Cfrac%7B%5BHAs%5E-%5D%5BH%5E%2B%5D%7D%7B%5BH_2Asc%5D%7D)


Solving for x:
x = 0.000702 M
![[HAsc^-]=0.000702 M](https://tex.z-dn.net/?f=%5BHAsc%5E-%5D%3D0.000702%20M)

Initially
x 0 0
At equilibrium ;
(x - y) y y
![K_{a2}=\frac{[As^{2-}][H^+]}{[HAsc^-]}](https://tex.z-dn.net/?f=K_%7Ba2%7D%3D%5Cfrac%7B%5BAs%5E%7B2-%7D%5D%5BH%5E%2B%5D%7D%7B%5BHAsc%5E-%5D%7D)


Putting value of x = 0.000702 M


![[Asc^{2-}]=5.92\times 10^{-8} M](https://tex.z-dn.net/?f=%5BAsc%5E%7B2-%7D%5D%3D5.92%5Ctimes%2010%5E%7B-8%7D%20M)
Total concentration of ![[H^+]=x+y=0.000702 M+5.92\times 10^{-8} M=7.0206\times 10^{-4} M](https://tex.z-dn.net/?f=%5BH%5E%2B%5D%3Dx%2By%3D0.000702%20M%2B5.92%5Ctimes%2010%5E%7B-8%7D%20M%3D7.0206%5Ctimes%2010%5E%7B-4%7D%20M)
The pH of the solution :
![pH=-\log[H^+]](https://tex.z-dn.net/?f=pH%3D-%5Clog%5BH%5E%2B%5D)

Maglev trains were created to connect Shanghai Pudong International Airport to Central Pudong. Transrapid, another name for the Maglev train is said to be the fastest train. It can run up to 270/mph in just eight minutes.
Compared to other transportation systems, Transrapid is faster and more cost effective. It has less maintaining coverage and zero sounds compared to the ordinary ones.
This kind of train is one of the most effective means of transportation. It lessens traffic and pollution caused by car emission. It also saves more time for people who are always on the go.