35. prepared and ate food

36. researchers can determine the knives via kind by bones of animals remained

Indrect evidence

37. Chemical signature on bones

38. food sticking to teeth

39. fossil was not easily found because ... is extremely common

40. investment is risky, which can be natural disasters, political event, or people’s climat

Part4 食物和儿童健康

31-40 completion

31. survey for ingredients

32. stored food quality

33. food saved should take into account of cooking temperature changes

34. pay attention to organic food in American market

媒体的Mass Medias’s disadvantages

35. supermarkets use price and image to attract customers

36. the source of the information

37. prime motivation for companies: only concern for sales

38. facilities such as for entertainment activities

39. food safety and nutrition

40. healthy choices depend on the lectures to parents

Part4 天然建筑材料的讨论 Natural building materials

31. 不是所有的建筑材料都是100%天然的，因为需要a good foundation 

earth 建筑

32. 这种材料包含高浓度的 large amount of sand

泥砖建筑

33. 包含大量的 lots of clay

34. advantages: cheap and convenient

35. 工人不需要很多的training

36. disadvantages: a lot of water, time and labour are required

草料建筑in US

37. 这种建筑最先建造的部位是roof

38. 用XXXXcovered to keep our the insects

Bamboo建筑

39. advantages: has good strength

40. disadvantages: easily catch the fire

Part4 雨伞的发展史 the history of umbrella

31. symbol of power of rulers

32. only rich Roman women can own it 

33. China made of silk - India made by bone and wood

34. wax function water proof

35. protect body with more early days

36. just use it with like a large lids

37. along with gloves

38. 1850s made of plastic

39. England made of steel

40. Germany made of nylon