Volcanoes form above subduction zones because Subduction zone volcanism occurs where two plates are converging on one another. One plate containing oceanic lithosphere descends beneath the adjacent plate, thus consuming the oceanic lithosphere into the earth's mantle. This on-going process is called subduction.
Answer:
a) 
b) 
c) 
d) 
Explanation:
Given:
- velocity of the sound from the source,

- original frequency of sound from the source,

- speed of the source,

(a)
We know time period is inverse of frequency:
Mathematically:



(b)
Distance travelled by the motorcycle during one period of sound oscillation:



(c)
The distance travelled by the sound during the period of one oscillation is its wavelength.



(d)
observer frequency with respect to a stationary observer:
<u>According to the Doppler's effect:</u>
...........................(1)
where:
are the observed frequency and the velocity of observer respectively.
Here, observer is stationary.

Now, putting values in eq. (1)


<span>D is the correct answer. If you wanted to know how fast a tiger can run, you would use meters and seconds. Meters will tell you the distance that the tiger ran and seconds will tell you how quickly the tiger ran the distance.</span>
Answer:

Explanation:
As the Universe expands, the photons of the cosmic microwave background increase its wavelength, making its temperature inversely proportional to the scale factor of the Universe. That is, as the average distances between galaxies increase, the temperature of the cosmic microwave background decreases by the same factor. Therefore, the temperature when the distances between galaxies are 1.7 times as large as they are today will be:

Answer:
Water is the solvent, therefore (B
Explanation:
Water is called the "universal solvent" because it is capable of dissolving more substances than any other liquid.
This has to do with the polarity of each water molecule. The hydrogen side of each water (H2O) molecule carries a slight positive electric charge, while the oxygen side carries a slight negative electric charge. This helps water dissociate ionic compounds into their positive and negative ions.