The protein efficiency ratio (PER), an indication of a protein's ability to support protein synthesis, is defined as the
A. expression of the percentage of nitrogen retained for maintenance and growth compared with the amount absorbed.
B. expression of the percentage of retained nitrogen compared with the amount ingested.
C. comparison of the amino acid balance of a food protein with the amino acid requirements of preschool-age children and then corrected for digestibility.
D. measure of a protein's ability to support growth.