From whom did David learn his survival skills?

In this section, you will hear a monologue. The monologue will be read twice. After the monologue, there will be a one-minute pause. During the pause, read the questions and the four choices marked A, B, C and D, and decide which is the best answer. Then mark the corresponding letter on the answer sheet with a single line through the centre.
     (M)Good evening and thank you for coming to find out about the Hillside Survival School. My name’s David Johnson. I started the school and I’m the school’s chief instructor. I learned my survival skills while I was in the army and since then I’ve used them all over the world.
    Before starting the Hillside Survival School, I worked in other well-known survival schools. My real aim for this school is to help people discover nature and outdoor life, and also to learn to have fun. We run a variety of courses but our basic survival course lasts a weekend and takes place throughout the year. This course teaches you the basic skills that you need to survive in the wilderness , and during the course you have a lot of opportunities to practice these skills. This course costs ￡139 per person.
    If you want an even bigger challenge, our extreme survival course takes place between November and February when the conditions are more difficult. These courses also last for a weekend and costs ￡149 per person.
    The extreme survival course teaches you to survive in a cold and wet environment. The course offers you the chance to push yourself, both physically and mentally. No tents, no gas cookers, just you and the wilderness. You learn to find and prepare food and cook it over an open fire. You learn to built a shelter and then you actually sleep in it. Most importantly, you learn a lot about yourself and how well you can cope with unexpected situations.
    A few final practical details. You have to be at least 18 years old to come on the courses. The full cost of the course needs to be paid at least 4 weeks before the course begins and remember that there are discounts for groups of 4 or more.