Choose the agreement that must be in writing in order to be enforceable: Select one: a. Arya agrees to sell camping supplies to Igor for $25. O b. Ivan agrees to provide housecleaning services to Natasha for $250 per month. c. Sarah executes a guarantee of the debts of her business, Sarah's Baked Delights Ltd., in favour of XYZ Bank, d. In December, 2020, a greenhouse agrees to supply flowers and shrubs for July 1 celebrations in 2021