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5.
Which of the following is not a mineral?
A. magnesium
B. calcium
C. oxygen
D. iron

answer: option (b) is the correct answer.

explanation:

intensive property is the physical property which does not depend on the size of system or amount of material present in system.

for example, color, density, melting point, boiling point etc are all intensive properties.

thus, we can conclude that the boiling point and color of a substance are both examples of intensive properties because they do not depend on the amount of matter in the sample.

answer;

18.5 seconds

explanation;

velocity is distance covered per unit time; it is given by displacement divided by time.

thus; time = displacement/velocity

total time = total displacement/velocity

total distance = 5000 meters south

total time = 5000/4.5

                  = 1111.11 seconds

but; 1 minute = 60 sec

thus; 1111.11 /60

                = 18.51 seconds

thus; the time taken is 18.5 seconds