|Question 20Verbal

Source Texts

Text
At 1,723 years old, KET 3996, a limber pine (Pinus flexilis) located in the United States. is one of the oldest known trees in the world. With almost two millennia of climate data in its tree rings, a single tree like______claims dendrochronologist Valerie Trouet, can tell the history of the world.
Which choice completes the text so that it conforms to the conventions of Standard English?
this
A
thIs:
B
this,
C
this:
D