Which of the Following Tests Provides Useful Information in Making $\dot { V } / \dot { Q }$

Which of the following tests provides useful information in making the diagnosis of ARDS for patients with inconclusive results on traditional tests?

A) examination of bronchoalveolar lavage fluid (BALF)
B) measurement of mixed venous oxygen level
C) measurement of total white blood-cell count
D) ventilation/perfusion ratio ( $\dot { V } / \dot { Q }$ ) scanning