|Question 21Verbal

Source Texts

Text
The relationship between grassland arthropod populations and agricultural fertilizers containing macronutrients-such as nitrogen, phosphorus, and potassium-was the focus of a 2000 study in the _blank by the researcher Mark E. Ritchie, the study examined a variety of arthropod specimens, which had been collected with sweep nets.
Which choice completes the text so that it conforms to the conventions of Standard English?
United States led
A
United States, led
B
United States. Led
C
United States and led
D