Walking is the easiest and simplest form. of exercise. By putting one foot in front of the

other, you can start to walk your ways towards a healthier lifestyle. Walking is an easy way to challenge the cardiovascular(心脏血管的)system while at the same time building muscles. But to achieve these goals, a little more than a gentle walk around the block is required.

Walking actually bums as many calories as running the same distance—if done in the correct manner and at a reasonable pace.

Start with a basic program that you can complete three or four times a week. This should include five main steps:

1) A beginning warm-up for about 5 minutes.

2) A little bit faster period of 5 minutes at medium level.

3) A 10-minute" burning" at a high level.

4) A 5-minute cool down period at a low level again.

5) A suitable walking pace of around 5 kilometers per hour will bum around 80 calories in 30 minutes.

According to the passage, walking is a simple way to ______.

A．lose weight

B．cure blood diseases

C．avoid heart attacks

D．strengthen heart functions