The tests, apart from a few personal and anthropometric data included to make possible a comparison between physical and mental endowment, fall naturally into (a) the senses, (b) the motor capacities, and (c) the more complex mental processes. Certain general desiderata may, perhaps, be suggested as applicable to each of these groups. It is well to have each test give information regarding a single or very limited group of powers; specific typical tests are better than general ones. _________________
Option (a) is the logical continuation of the passage as the passage is talking mainly about testing in parts and since the part on the senses is marked as ‘a’ it could be logically taken as the continuation of the passage.