Why Is Research on Language Comprehension Easier to Conduct Than

Why is research on language comprehension easier to conduct than research on language production?

A) Language comprehension occurs more frequently than language production.
B) Language comprehension can be studied with participants of all ages, whereas language production can only be studied in older children and adults.
C) Language comprehension is more overt, whereas language production is more covert.
D) It is easier to manipulate a variable that can influence language comprehension than it is to manipulate a variable that can influence language production.