Answer to this is copper wire
Answer:
I feel it's to easily differentiate the positive from the negative...... like in gram staining of bacteria, the colour tell us which bacteria is gram positive or gram negative...... I just feel that this is science and it is advisable to know what the opposite result of an experiment should look like.
M I think the answer is a run on sentence
B) the selection for different shaped beaks that best suit different niches
