Tammy is using a treadmill, and when she puts her hands on the bar, sensors read her heart rate. today, the sensors are telling tammy that she is reaching 183, which is the highest rate in her target zone. what should she do to get the most effective workout?

Increase her running speed without adjusting the incline
Use the machine to maintain or decrease her intensity
Do additional aerobic exercises immediately after the treadmill
Use the machine to increase the incline and intensity

Here are the given choices for the said question.
Well, the answer would be - Use the machine to increase the incline and intensity -
Because the higher the incline the more effort you give, thus your heart rate also increase.