In the last 60 years, the world’s population has 1

.______ from 2.5 billion in 1950 to over 7 billion.Food became a big problem as we were not able to feed everyone.Now the world’s population is 2.______ to continue growing and may 3.______ 11 billion by 2100.So in a world 4.______ nearly 1 billion people already do not have enough food, can we really feed another 6 billion？ Population growth is not the only reason for food shortages.Our diet is also to 5.______ for it.Nowadays, with increasing numbers of people living in cities, we tend to eat more meat.To produce meat we have to use a lot more land and water to grow the food for the animals.And we also need more energy to process the meat.As a result, we are using more land and resources to actually produce less food.We could feed the growing population easily if everyone became a 6.______.But who would make this change？ Would you give up meat to feed others？ Innovative solutions to this problem are being used and researched around the world.One idea being tried is 7.______ farming, which is to build farms in very tall buildings in the centre of cities.Such farms require less space.They also reduce the distance the food needs to travel to 8.______ most people.Another 9.______ idea is the “seeds in space” project organised by the Chinese Academy of Sciences.

Actually, our senses and memories are more connected than we think.Researchers have discovered 10.______typically, a strong connection between smells, emotions and life experiences is 11.______before age 5.This is 12.______ true for smells that we don’t smell every day.But even in 13.______, links are made between smells and memories.You might make a connection between a 14.______ and a friend or lover, or the smell of a certain food may take you back to the first time you ate it.The reason time 15.______ to go more quickly as we get older is that we repeat the same 16.______ and experience the same events over and over.Doing things for the first time usually leaves a strong memory.Remember your first day of school or a new job？ But as we repeat those 17.______, strong memories aren’t created, and time goes quickly.You heard a song on your way to campus, and you found it hard to get rid of it for the rest of the day.Songs that 18.______ in your head all day are known as “earworms”.It was found in one study that nearly 92% of people have such an experience once a week or more.Earworms are started by many different kinds of things, such as going back to the same place 19.______ you first heard a song.People also often listen to sad music when they are in a sad 20.______, and stressful situations often remind them of that song.

Knowing what you value most is only the first step.Sometimes in reality, we cannot find a job that satisfies all our needs or is perfect in every way.If we have too much of one thing and not enough of another, we are unlikely to be satisfied.Finding a balance between the factors and deciding what to give up is even more important.

A.where

B.mood

C.forecast

D.innovative

E.vertical

F.hit

G.tripled

H.perfume

I.where

J.stay

K.that

L.adulthood

M.blame

N.vegetarian

O.routines

P.formed

Q.reach

R.particularly

S.seems

T.events