I have two questions that I'm not quite sure on.

In the sentence 'To Franklin, publishing was a challenging and rewarding career', which word is a gerund?

a.publishing
b.challenging
c. rewarding
d. career

In the sentence 'Benjamin Franklin enjoyed experimenting with electricty and inventing tools used by many people' which word is a participle?

a.experimenting
b.invented
c.used
d.inventing

A gerund is a verb form ending in -ing. Gerunds are used as nouns. They can be subjects or objects.
Which word in your first sentence do you think is a gerund?

Participles are also verb forms, but they are used as adjectives. Which word do you think is the participle?

Please post your answers and we'll be glad to comment on them.

1. Publishing
2. experimenting

Could these be correct?

The first one is absolutely correct. However in the second one, experimenting is a gerund. What word describes "tools"

So would it be used?

Yes, "used" is correct.

=)

Yes, "used" is correct. In the sentence "Benjamin Franklin enjoyed experimenting with electricity and inventing tools used by many people," the word "used" is a participle. It is a verb form ending in -ed and is used as an adjective to describe the tools. Well done!