Answer:

answer is option b

Explanation:

velocity is distance upon time...

time is given in milliseconds so convert to seconds... 1second = 1000milliseconds

so the wave speed = 3/4 milliseconds

= 3 × 1000/ 4

= 3000/4

=750 m/s

we get this answer since we must convert milliseconds to seconds (looking at the units in the options)

also 3m is the wavelength given... 1 wavelength is over 4 milliseconds so we take time as 4 milliseconds

hope it helps

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