Breakwaters protect an anchorage from the effects of weather and longshore drift, while jetties protect against erosion, by keeping the waves from sweeping the sand away. Difference, they both protect against different things.
Answer: B. providing access to objects that are hard to find
Explanation: A specimen can be simply refered to as a sample of blood, tissue, fluid or a piece of a matter which scientist take or obtain to have a better look (study) at it in a lab.
Specimen collection is the process involved in getting or obtaining these samples for better analysis in a lab. This process help scientist get, obtain or have access to samples or objects that are not easily accessible.
Therefore Specimen collection helps scientist carry out experiment by providing access to objects that are hard to find.
B) Commensalisms is the right answer
Answer: D. Iron rusts
Explanation: Rust is made from different chemicals in the air that come in contact with said metal. That could be acidic rain for example. Water freezing is only changing temperature. Sugar dissolving is breaking down molecules. Salt and pepper mixed in a dish is a physical change (also that's just plain evil to some people but that isn't the point). Your answer will be D. Iron rusts.
Hope this helps!