Read the following passage about the human eye and answer the question. According to the passage, what is the average rate at which the human eye blinks?

Introduction / Context:
The passage on the human eye not only explains how vision works but also mentions an interesting fact about blinking. It describes how blinking helps wash the eye with the salty secretion from the tear glands. The question asks for the average rate of blinking mentioned in the passage.

Given Data / Assumptions:

• The passage states that human eyes blink an average of once every six seconds.
• This blinking action spreads the salty secretion from the tear or lachrymal glands across the eye.
• The tear glands are located behind the upper eyelid at the outer corner of the eye.
• The liquid is later drained into the nose through the tear duct at the inner corner of the eye.
• The question focuses only on the numerical rate of blinking.

Concept / Approach:
This is a straightforward detail question that tests careful reading of a numerical fact. The candidate must remember or locate the exact statement containing the word “blink” and the associated time interval. There is no need for calculation, only recognition and correct selection from similar sounding options.

Step-by-Step Solution:

Verification / Alternative check:
We can check that the other options all change the rate in different ways. If a person blinked six times every second, that would be an extremely high and unrealistic rate. Six times every six seconds would average one blink per second. Once every second is also faster than the rate given in the passage. Therefore, the only choice consistent with both the passage and normal experience is blinking once every six seconds.

Why Other Options Are Wrong:

• Option a: Six times every second is far too frequent and is not stated in the passage.
• Option c: Six times every six seconds changes the rate and does not match the exact wording.
• Option d: Once every second is more frequent than what the passage states and therefore incorrect.

Common Pitfalls:
Examinees sometimes misread numbers under time pressure, especially when several options look similar. Confusing “once every six seconds” with “six times every six seconds” is a common mistake. To avoid this, it is important to slow down briefly when reading numerical information and to match the option word for word with the statement in the passage.

Final Answer:
Once every six seconds is the correct answer, as the passage clearly states that this is the average blinking rate of human eyes.