Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.

Ex Input:
Context: The 10th Cavalry returned from the Philippines in late 1902 and settled down in different posts in the south western United States. Patrols and garrison life was the routine for the regiment. Under war plans, the 10th was designated for service in the Pacific and support in the Philippines from 1915 through 1942 but never rotated there. The 9th Cavalry Regiment became "Park Rangers" in 1905 for Yosemite National Park and other state and federal lands. The Troopers' Campaign Hat, sporting the "Montana Pinch" used to help shed the tropical downpours. That "Montana Pinch" gave the hat the distinctive look we recognize today as the "Smokey Bear Hat". 
 Question: Which cavalry is credited with the Smokey Bear Hat, 10th or 9th?

Ex Output:
9th cavalry regiment


Ex Input:
Context: Mary Ball was born in 1812, the second daughter of Bob Stawell Ball and his wife Mary nee Green. 
 Question: Who was the male parent of Mary Ball?

Ex Output:
bob stawell ball


Ex Input:
Context: The subventricular zone (SVZ) is an embryonic remnant that persists and remains mitotically active throughout adulthood. The rodent SVZ harbors neuronal precursors, principally in its anterior part, and generates neuroblasts that migrate tangentially into the olfactory bulb, thus forming the so-called rostral migratory stream. This study aimed at characterizing the SVZ in the human brain. Antibodies raised against the widely used SVZ molecular markers nestin, glial fibrillary acidic protein, beta-tubulin-III and polysialylated neural cell adhesion molecule, have allowed us to characterize in detail a zone similar to the rodent SVZ in humans. Virtually all portions of the lateral ventricle, as well as the ventral (hypothalamic) sector of the third ventricle, displayed immunoreactivity for most of the molecular markers. The midline region of the septum (septal recess) and the ventral portion of the SVZ displayed a particularly intense immunostaining for all SVZ markers. These two regions may represent zones of adult neurogenesis that are unique to primates. Furthermore, the anti-apoptotic protein Bcl-2 was found to be actively synthesized and co-expressed with all the other markers throughout the entire SVZ. This study reveals that a well-developed SVZ exists in the adult human brain and suggests that Bcl-2 might play an important role in the functional organization of such a system. 
 Question: Which intermediate filament (IF) protein can be used as a non-specific marker of the neuronal precursor cells of the subventricular zone?

Ex Output:

nestin