Discuss why a physically active job does not guarantee better physical fitness.

Like a personal trainer? Personal trainers don't do a lot of physical activity, they mostly warm up their clients and tell them what kind of workouts to do. But their are also coaches, and they don't do much either. So you're not benefiting much out of that. 

Iwould put 'think' in the blank

Subtract your 2-minute heart rate from the heart rate you took immediately after exercising. the faster your heart rate recovers (or slows down ) the fitter and healthier your heart. if the difference between the two numbers is: less than 22: your biological age is slightly older than your calendar age