The rise time (tr) is the time it takes for a pulse to rise from its ________ point up to its ________ point. The fall time (tf) is the length of time it takes to fall from the ________ to the ________ point.

• 10%, 90%, 90%, 10%
• 90%, 10%, 10%, 90%
• 20%, 80%, 80%, 20%
• 10%, 70.7%, 70.7%, 10%