I believe the answer is a and d and b not 100% sure
<h2>Answer:</h2>
Bella is writing a research paper on ocean currents. The two sources she should consult will be;
1. an article published by a university or a government agency
3. an article published in 2015 and updated a week ago
Because while writing research papers we should consult authentic and latest information and resources.
It's the pull of gravity on an object.
Hope this helps!