Microorganism motile at 25deg C but not motile at 37deg C-
Listeria monocytogens
Campylobacter
Yersinia pestis
Streptococcus agalctiae
Ans. is 'a' i.e., Listeria monocytogens Listeria monocytogens exhibits characteristic, slow, tumbling motility when grown at 25degC but at 37degC it is non motile.