1. Hot weather makes the heart pump harder. That is the reason why the majority of mountain rescue statistics are made up from summer walkers suffering heart attacks. So, how to walk safely in summer?

2. The answer is to keep up the water intake. It is vital not to wait until a thirst before stopping for a drink. Instead, keep drinking regularly from your water bottle.

3. Given that evaporation is the body's way to cool itself, soaking a hat with water is a great way to cool the head. Walking in the heat increases the rate at which your feet swell, which can lead to them feeling tight in your boots. Cool water from a stream reduces any swelling and helps general foot comfort.

4. As for what clothing you wear, this should be lightweight and reasonably loose-fitting. Tight clothing will feel uncomfortable and may even lead to an irritating rash on the skin. The answer, if this does develop, is to try and stay cool as much as possible. Do this by either keeping in the shade, or washing the affected area with cold water, but without soap.

5. It is understandable to want to remove some clothing when it is extremely hot, but it does not really make much sense to take off T-shirts. The sun's rays can be quite strong, and shoulders are always very sensitive to sunburn. This is the worst place to be red and sore when you are wearing a heavy rucksack on your back. Wearing shorts can also create problems for walkers, as the backs of the legs can catch the sun very easily.

From the 20th to the 21st century, there have been (1) _______ significant changes in the majority of countries around the world. Substantial differences are evident between the way we live today (2) _______ the way we lived a century ago. Vietnam is no exception although there are some aspects of life in Vietnam that are similar to the way of life of the twentieth century.

Living in Vietnam today differs greatly (3) _______ the lifestyle of 100 years ago. People in the past mainly worked in agriculture whereas today there are significantly fewer people working in this (4) _______ of the economy. These days, by comparison, people are more likely to be employed in manufacturing and tourism than in the rice fields. Moreover, Vietnam, (5) _______ was traditionally agricultural, is transforming into an entirely different country. While agriculture is still an important component of the Vietnamese economy, other enterprises are accounting for an increasing amount of economic activity.