Question: Symbiosis played a major role in the co-evolution of flowering plants and the animals that pollinate them. Many plants that are pollinated by insects, bats, or birds have highly specialized flowers modified to promote pollination by a specific pollinator that is also correspondingly adapted. The first flowering plants in the fossil record had relatively simple flowers. Adaptive speciation quickly gave rise to many diverse groups of plants, and, at the same time, corresponding speciation occurred in certain insect groups. Some groups of plants developed nectar and large sticky pollen, while insects evolved more specialized morphologies to access and collect these rich food sources. In some taxa of plants and insects the relationship has become dependent, where the plant species can only be pollinated by one species of insect.
Is there an answer to this question: What gave rise to a select group of plants?

Answer: unanswerable

Question: In general relativity, a vanishing stress-energy tensor implies, through Einstein field equations, the vanishing of all the components of the Ricci tensor. Vacuum does not mean that the curvature of space-time is necessarily flat: the gravitational field can still produce curvature in a vacuum in the form of tidal forces and gravitational waves (technically, these phenomena are the components of the Weyl tensor). The black hole (with zero electric charge) is an elegant example of a region completely "filled" with vacuum, but still showing a strong curvature.
Is there an answer to this question: What has no electric charge?

Answer: black hole

Question: Wilhelm Erb's (1874) "intensive" theory, that a pain signal can be generated by intense enough stimulation of any sensory receptor, has been soundly disproved. Some sensory fibers do not differentiate between noxious and non-noxious stimuli, while others, nociceptors, respond only to noxious, high intensity stimuli. At the peripheral end of the nociceptor, noxious stimuli generate currents that, above a given threshold, begin to send signals along the nerve fiber to the spinal cord. The "specificity" (whether it responds to thermal, chemical or mechanical features of its environment) of a nociceptor is determined by which ion channels it expresses at its peripheral end. Dozens of different types of nociceptor ion channels have so far been identified, and their exact functions are still being determined.
Is there an answer to this question: Who came up with the intensive theory in 1784?

Answer: unanswerable

Question: As many Japanese had feared, Japan's supply arrangements could not maintain her forces. Once Mutaguchi's hopes for an early victory were thwarted, his troops, particularly those at Kohima, starved. During May, while Mutaguchi continued to order attacks, the Allies advanced southwards from Kohima and northwards from Imphal. The two Allied attacks met on 22 June, breaking the Japanese siege of Imphal. The Japanese finally broke off the operation on 3 July. They had lost over 50,000 troops, mainly to starvation and disease. This represented the worst defeat suffered by the Japanese Army to that date.[citation needed]
Is there an answer to this question: How many troops had the Japanese lost?

Answer:
50,000