19. According to the passage, which of the following statements is true?
(A) The development of wilderness to agricultural land can save bumblebees.
(B) Bumblebees and non-native bees can complement each other perfectly.
(C) Scientists use big data and modeling to investigate the decrease of bumblebees.
(D) Since bumblebees can produce heat by themselves, they are not sensitive to weatherfluctuations.