Final answer:
Water and grass are the two items in the marsh that are good at keeping secrets.
Step-by-step explanation:
In the given question, the phrase 'good at keeping secrets' suggests that the student is referring to objects in the marsh that can hide or conceal information. Based on the provided information, two items in the marsh that are good at keeping secrets are water and grass.
Water in the marsh can hide various objects beneath its surface, making them difficult to find or detect. For example, an item dropped in the marsh may sink into the water and not be easily visible.
Similarly, grass in the marsh can provide cover or concealment for hidden objects. The dense vegetation can make it challenging to locate items among the plants.