6because the actions of other road users are you can lower your risk if you adequately communicate to those around you. always signal your intention to change lanes or turn.

Because the actions of other road users are unpredictable, you can lower your risk if you adequately communicate to those around you. Always signal your intention to change lanes or turn.

Explanation:

Actions of other drivers are unpredictable that's why it is important to drive defensively  and always signal your intention to change lanes or turn.

The best answer to fill in the blank in this case, would be: Because the actions of other road users are: unpredictable, you can lower your risk if you adequately communicate to those around you. Always signal your intention to change lanes or turn.

Explanation:

We are all individuals, we all think and act in different ways and the only manner in which others can know what we are thinking, what we are feeling, or how we plan to act, is through communication, both verbal and non-verbal. In driving, this is particularly important as communication is further impeded by the absence of direct contact between people. This is why signs and signals are used. And because you cannot tell what another person is going to do while driving, is why you use these signs to communicate. This lack of knowledge on how a person will act, is known as unpredictability, and signaling prevents accidents by communicating intention through non-verbal gestures.

i think it is the third one.