Final answer:
Paddlers should avoid waterfalls, whirlpools, and waves when navigating rivers as they pose serious hazards. These elements can lead to physical danger, including injury or drowning. Safety and strategic paddling near the shore or in the middle of the river also play important roles in effective and secure paddling. Option B is correct.
Step-by-step explanation:
The three river hazards that paddlers should avoid are B) Waterfalls, whirlpools, waves. These elements present clear dangers to paddlers navigating river systems. Waterfalls represent a clear physical danger and should be avoided to prevent injury or death. Whirlpools, which can form in varying sizes, create dangerous currents that can pull a watercraft under or throw it into a dangerous situation.
Lastly, waves, especially large or unpredictable ones, can overturn boats or throw paddlers from their craft, leading to potential injury or drowning.
When choosing a study site such as a river, one must consider accessibility and potential problems like tides and rain which could affect safety and the study conditions. Additionally, paddling strategies differ depending on whether you're going upstream or downstream—near the shore is often recommended when going upstream due to weaker currents, whereas the middle of the river can be better when heading downstream to avoid obstacles closer to the banks.