Answer: a) needs more light when reading.
Step-by-step explanation:
According to the question, as Lewis is 70 year old, he might be experiencing general old age issues that tends to occur such as weakening of hearing power, lower eye-sight, weaker bones, low stamina and ability to perform task rapidly etc.
Therefore,Lewis might be experiencing more requirement of light while reading due to weakening of eye-sight due to aging effect.
Other options are incorrect because lower neural connection,catching flu or all the problem are not experienced by Lewis. Thus, the correct option is option(a).