What does it mean to cause source biased? why can bias
take away the credibility of the source?

To cause a source to be biased means that it is influenced by your opinion or another factor that is not factual. Bias can take away from the credibility because it is not completely true, as a source should be.

hello,

what started the norman conquest?

profound political, administrative, and social changes in the british isles. last line of my information: )

(d) take jobs from american workers.