In the Grinblatt-Titman (GT) Performance Measure

In the Grinblatt-Titman (GT) performance measure,

A) portfolio performance is measured by assessing the quality of services provided by money managers by looking at adjustments made to the content of their portfolios.
B) portfolio performance is measured by examining both unsystematic and systematic risk.
C) portfolio performance is measured by comparing the returns of each stock in the portfolio to the return of a benchmark portfolio.
D) portfolio performance is measured on the basis of return per unit of risk.
E) portfolio performance is measured on the basis of historic average differential return per unit of historic variability of differential return.