Understanding the question:
The question is asking for the decimal equivalent of a second in terms of an hour.

Solution:
To find the decimal of an hour that a second represents, we need to convert the time units to the same format.

- There are 60 seconds in a minute.
- There are 60 minutes in an hour.

Converting seconds to hours:
To convert seconds to hours, we need to divide the number of seconds by the number of seconds in an hour.

- 1 hour = 60 minutes * 60 seconds = 3600 seconds

Therefore, to find the decimal of an hour that a second represents, we divide 1 second by 3600 seconds.

1/3600 = 0.000277778

Comparing the options:
Now, let's compare the result we obtained with the given options:

a) 0.0025
b) 0.0256
c) 0.00027 (Correct Answer)
d) 0.000126

The correct answer is option 'C' (0.00027), which matches the result we obtained.

Explanation:
A second is a very small unit of time. When expressed as a decimal of an hour, it becomes an extremely small decimal. In this case, the decimal equivalent of a second is 0.00027 of an hour. This means that it would take approximately 3,600 seconds to make up one hour.

It's important to understand the relationship between different units of time and their decimal equivalents in order to make accurate conversions.