Could a fungal parasite have caused some of the many amphibian population declines and extinctions in recent decades? one study found that the number of yellow-legged frogs (rana muscosa) plummeted after the chytrid batrachochytrium dendrobatidis reached the sixty lake basin area of california. yellow-legged frogs can be killed by b. dendrobatidis infection. in the years leading up to the chytrid's 2004 arrival, there were more than 2, 300 frogs in these lakes. by 2009, only 38 frogs remained; all the survivors were in two lakes (yellow) where researchers had applied a fungicide to reduce the chytrid's impact. do the data indicate that the chytrid caused or is correlated to the drop in frog numbers? a. the data suggest that the chytrid caused the decline because populations in areas without the chytrid are thriving, whereas populations exposed to the chytrid have gone extinct. b. the data suggest that chytrid fungi are only correlated to frog population declines because in many lakes, the chytrid appeared only after frog populations had already declined. c. the timing of the declines and the survival of frogs treated with fungicides suggest that the chytrid caused the decline in frog populations. d. there is no evidence that chytrid fungi directly harm frogs, suggesting that the fungi are only correlated to frog population declines.