Final answer:
The phrase "Yo sé que..." is in the indicative mood and means "I know that...".
Step-by-step explanation:
The phrase "Yo sé que..." is in the indicative mood. The indicative mood is used to state facts or opinions. In this case, the speaker is stating something they know. The phrase "Yo sé que..." means "I know that..." and is followed by a clause expressing the thing the speaker knows.