Answer :
The words showing contrast can be found here:
"On the other hand, seagulls are scavengers, while wild geese aren't. "
and here "while" is the word that shows the contrast
"Seagulls, for example, are often found around garbage dumps. Geese, however, feed on things like seeds and insects."
Here we have the word "however" to show the difference
So the correct answer is C: while and however!
"On the other hand, seagulls are scavengers, while wild geese aren't. "
and here "while" is the word that shows the contrast
"Seagulls, for example, are often found around garbage dumps. Geese, however, feed on things like seeds and insects."
Here we have the word "however" to show the difference
So the correct answer is C: while and however!