tn The verb צָעַק (tsa’aq) is used for prayers in which people cry out of trouble or from danger. U. Cassuto observes that Moses would have been in real danger if God had not answered this prayer (Exodus, 103).
tn The verb is an unusual choice if it were just to mean “brought on.” It is the verb שִׂים (sim, “place, put”). S. R. Driver thinks the thought is “appointed for Pharaoh” as a sign (Exodus, 64). The idea of the sign might be too much, but certainly the frogs were positioned for the instruction of the stubborn king.