Look at http://owl.english.purdue.edu/handsouts/interact/eslprepEX1.html
General Exercise on Prefixes
Complete the given stems with the prefix which means the same as the word in brackets. There is an explanation to guide you.
1. ____thermia (below, lower) = a serious medical condition in which a person's body temperature falls below the usual level. ( hypo -)
2. ____sexual (the same) = a person who is sexually attracted to people of the same sex and not to people of the opposite sex. ( homo-)
3. ____sexual (not, without) = without sex, sexual organs or sexuality, or not interested in sexual relationships. ( a - )
4. ____present (all) = present or having an effect everywhere at the same time.
( omni- )
5. ____physics (star, space) = the type of astronomy which uses physical laws and ideas to explain the behaviour of the stars. ( astro - )
6. ____ology (people) = the study of the human race, its culture and society and its physical development. ( anthrop - )
7. ____morphism (people) = the showing or treating of animals, gods and objects as if they are human in appearance, character or behaviour. ( anthropo - )
8. ____metrical (with, together) = having similarity in size, shape, and relative position of corresponding parts. ( sym - )
9. ____meter (time) = a piece of equipment which measures time very accurately.( chrono - )
10. ____lexia (abnormal, ill) = a difficulty with reading and writing caused by the brain's inability to see the difference between some letter shapes. ( dys - )
11. ____genous (the same) = consisting of parts or people which are similar to each other or are of the same type. ( homo - )

12. ____function (abnormal, ill) = a problem or fault in an organ or machine. ( dys - )
13. ____ficial (good) = tending to promote physical well-being. (bene - )
14. ____factor (good) = someone who gives money to help an organization,society or person. ( bene - )
15. ____etics (sound) = the study of the sounds made by the human voice in speech.
( phon - )
16. ____economics (large) = the study of financial systems at a national level
( macro - )
17. ____dermic (below, lower) = this kind of needle is used to inject drugs under a person's skin. ( hypo - )
18. ____cosm (large) = any large organized system considered as a whole, rather than as a group of smaller systems. ( macro - )
19. ____biosis (with, together) = a relationship between two types of animals or plants in which each provides for the other the conditions necessary for its continued existence. ( sym - )
20. ____archy (mother) = a type of society in which women have most of the authority and power. ( matri - )