23. Mr. Trent, a cash-basis taxpayer, owns a residential rental house which he began renting to a tenant in December 2019. Mr. Trent received a $900 security deposit that is to be returned to the tenant at the expiration of his one-year lease. Mr. Trent also received $1,800 in December 2019, for the months of December 2019 and January 2020. On December 9th, the tenant paid $400 for heat pump repairs that were Mr. Trent's responsibility. What is the amount of gross rental income that Mr. Trent should include in his gross income for 2019? Select one: a. $1,800 b. $3,100 c. $2,700 d. $2,200