|Question 18Verbal

Source Texts

Text
When a soil is classified using the International Union of Soil Sciences' system, its similarity to each of the 32 soil reference groups—defined by several criteria—_______ evaluated, one group at a time, until a match is found. The comparisons are made in a specific order; thus, the criteria for lixisols (soils with clay-rich subsoil) are only applied if the soil doesn't match the criteria for ferralsols.
Which choice completes the text so that it conforms to the conventions of Standard English?
have been
A
are
B
is
C
was
D