What is bias? falsified data, resulting from pre-conceived ideas about the results racial prejudice on the part of the experimenters systematic error in the way a sample represents a population a situation in which two errors cancel one another errors resulting from getting two strange of a sample?

A bias is not literally a lie, so it is not data that is faked or made up in any way - instead, it's a real data. 

Also, bias can be racial- but it's not always racial, therefore, we can have a "racial bias"
 

The correct answer is:
systematic error in the way a sample represents a population 
 

A bias changes the results through choosing some part of the population that is not representative. For example, if we choose all the English teachers to represent all teachers, we might find that all the teachers think that English is the most important subject. 

Ghana, first of the great medieval trading empires of western africa (fl. 7th–13th century). it was situated between the sahara and the headwaters of the sénégal and niger rivers, in an area that now comprises southeastern mauritania and part of mali.

Idont understand the question