Answer:
a. Follows with certainty (necessarily)
Step-by-step explanation:
In a deductively valid argument, if the premises are true, then, the conclusion is necessarily true. It is impossible for a deductively valid argument to have false premises and and a true conclusion, or to have true premises and a false conclusion. It would not make sense.
An example of this type of argument would be:
If it rains, I will be carrying un umbrella. It's raining, therefore, I'm carrying un umbrella.