Answer
Correct Answer is a.(spikes)
Explanation:
option a is correct because here serves, rotation and spikes all the three words are using as object.
The volleyball team practiced their serves, rotations, and spikes.
option b cannot be correct because here spiking is used as a verb and sentence(The volleyball team practiced their serves, ) is in past indefinite form and we cant use word spiking here because this form of verb is used in continues form of sentences only.
Option c cannot be correct as because in this option ""spikes the ball" spikes is used as a verb which can be used in present indefinite form of sentence only but here sentence is in past indefinite form.
Again option d cannot be correct because in this option ""spikes over the net" spikes is used as a verb which can be used in present indefinite form of sentence only but here sentence is in past indefinite form.
C. Ptolemy argued that earth was the center of the universe
Answer:
a) The car was moving at a speed of 
b) The negative sign of 
denotes that the observer is coming towards the police car which is the source of the sound.
c) 
Explanation:
Given:
- original frequency of the source,
- speed of the source,
- velocity of the obstacle car be,
- speed of sound,
- observed frequency,
<u>Using the equation from the Doppler's effect:</u>
a)
The car was moving at a speed of
b)
The negative sign of denotes that the observer is coming towards the police car which is the source of the sound.
c)
Now when, 
Then, 
Using the Doppler's eq.:
Answer:
duty h gucuuvu h just hc i oicuxp o cut o icucj x uc jo 8cuc8c
