Imagine an active, employed sixty-year-old who does not have dementia. Which of the following statements offers an explanation why he might not be as good at forming memories as he was when younger? His brain is no longer making new neurons.
He has lost too many synapses through underuse.
He is not as emotional as he once was.
He has too many neurofibrillary tangles.

You isolate an infectious substance capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, viroid, or prion. you have four methods at your disposal to analyze the substance and determine the nature of the infectious agent.i. treat the substance with enzymes that destroy all nucleic acids and then determine whether the substance is still infectious.ii. microscope.iii. culture the substance on nutritive medium, away from any plant cells.iv. treat the sample with proteases that digest all proteins and then determining whether the substance is still infectious.if you already know that the infectious agent was either bacterial or viral, which method(s) listed above would allow you to distinguish between these two possibilities? a) ib) iic) ii or iiid) iv