Which of the following contracts need not be in writing?

A$.$ A teacher's contract for the $2020-2021$ school year running from August $2020$ to May $2021$ that was negotiated in February $2020.$

B$.$ A contract for the sale of a small tract of land for $$390.$

C$.$ An audit contract entered into in March $2020$ that requires completion of the audit ASAP but no later than April $2021.$

D$.$ A second mortgage from the same bank that handled the first mortgage on the same property.