Read the instructions for assembling a bicycle:
Step 1 - Unpack all the components from the box. Step 2 - Identify the different parts, such as the frame, wheels, and pedals. Step 3 - Attach the wheels to the frame using the provided nuts and bolts. Step 4 - Tighten all the bolts and screws to ensure the bicycle is stable.
Which of the following is a crucial step in ensuring the bicycle is safe to ride?