Answer:
C
Explanation:
An element is a pure substance that can not be broken down into anything simpler
A compound in also a pure substance held together in fixed proportion through chemical bonds
Answer:
The universal sign for choking is __________.
A.
two balled fists pressing the abdomen
B.
pointing at an open mouth
C.
two hands grasping the neck
D.
pretending to cough
Explanation:
Answer:

Explanation:
We know that speed is defined as distance moved per unit time hence expressed as
where v is speed in m/s, d is distance in m and t is time in seconds. Making d the subject of the above formula then

Substituting 343 m/s for d and 10 s for t then

Therefore, the distance between speaker and deter is 
Answer:

Explanation:
Given

<em>See comment for complete question</em>
Required
Calculate the frequency
Frequency is calculated using:

Where
speed of light


Convert wave length to meters


So, we have:



