A lost update occurs when

a. two transactions select the same row and then update the row based on the values originally selected
b. you perform an update on a set of rows when another transaction is performing an insert that affects one or more rows in that same set of rows
c. a transaction selects data that isn’t committed by another transaction
d. two SELECT statements that select the same data get different values because another transaction has updated the data in the time between the two statements