Let's understand the stem first:
Researchers measured intraocular across four years for thousands of teenagers.
They found that intraocular pressure increased faster for teenagers who used screens for over 6 hours a day.
It is a stated as a fact that intraocular pressure is linked to visual impairment.
Conclusion drawn: Higher screen usage leads to visual impairment.
Now let's look at the options:
A) The paragraph clearly speaks that researchers noted a FASTER INCREASE in intraocular pressure. The fact that the volunteers had elevated intraocular pressure at the start is immaterial as the comparison happens in terms of pace of increase, and not the final levels. Option invalid.
B) The statement clearly states that intraocular pressure IS linked to visual impairment. Hence, how reliable it is in comparsion with other metrics is imamterial. Option invalid.
C) This is interesting, if there are other habits that lead to increased intraocular pressure, this directly challenges the conclusion that screen time leads to visual impairment, as it can be a combination of screen time and a second habit (that increases intraocular pressure), or a different habit altogether (that leads to a greater increase in intraocular pressure) leading to visual impairment. We hold onto this option.
D) If it is indeed the case (let's say not sleeping enough also contributes) it does not negate the theory, it merely adds another layer to it. Eg: If the answer is YES, it will mean that this other factor as well as screen time lead to visual impairment. If NO, it would still mean that only screen time leads to visual impairment.
E) Visual impairment can indeed result from other factors (an accident, aging etc) The question does not say that visual impairment occurs ONLY due to intraocular pressure. The question says that it can speed it up.
(C) holds up the best.
Ans: (C).