Overview of Basic verb forms used in conditional sentences

The present participle is always invariable; the form never changes.USES: The progressive forms are used with verbs of action. The progressive stretches the time frames of the action. It is NOT used with ser, estar, tener, poseer, saber, conocer, poder.The present participle may be used alone to introduce a clause: Andando por la calle, la ... ................
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