Which earned value management (EVM) metric is a measure of the cost efficiency of budgeted resources expressed as a ratio of earned value (EV) to actual cost (AC) and is considered a critical EVM metric?

Which earned value management (EVM) metric is a measure of the cost efficiency of budgeted resources expressed as a ratio of earned value (EV) to actual cost (AC) and is considered a critical EVM metric?
Correct Answer : B