Final answer:
Statistics must be reasonably accurate and collected systematically. They are also aggregates of facts and are affected by a number of factors.
Step-by-step explanation:
One of the major characteristics of statistics is that statistics must be reasonably accurate (option c) in order to provide reliable information. Accuracy ensures that the data collected and analyzed is as close to the actual values as possible.
In addition, statistics must be collected systematically (option d) in order to ensure that the data is representative and unbiased.
On the other hand, statistics are aggregates of facts (option a) and are affected by a number of factors (option b). These are both major characteristics of statistics.