Which of the following sentences includes a non-restrictive clause?
a) Ronit knew that she enjoyed gardening, but she didn't realize how much she loved it until now.
b) Ronit learned a lot about gardening the first year at her new house.
c) Ronit really enjoyed gardening, so she bought a house with lots of land.
d) Ronit, who really enjoyed gardening, bought a house with lots of land for her dream garden.