The correct option is A Spikelet inflorescence
Oat is a member of Poaceae as it has spikelet inflorescence. Flowers of Poaceae are characteristically arranged in spikelets, each spikelet having one or more florets. The spikelets are further grouped into panicles or spikes. A spikelet consists of two (or sometimes fewer) bracts at the base, called as glumes, followed by one or more florets. A floret consists of the flower surrounded by two bracts, one externalthe lemmaand one internalthe palea.
Therefore, the correct option is A.