Final answer:
The grammatical form used in the sentence is present progressive. It indicates an ongoing action in the present.
Step-by-step explanation:
The grammatical form used in the sentence "En este momento ellos están jugando beisbol" is present progressive.
The present progressive tense is used to indicate an ongoing action in the present. In this sentence, the verb "estar" (to be) is conjugated in the present tense, and the verb "jugar" (to play) is in its present participle form "jugando" (playing).
For example, in English, the equivalent sentence would be "In this moment, they are playing baseball."
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