Read the excerpt from act 2, scene 1, of Julius Caesar.

BRUTUS. The exhalations whizzing in the air
Give so much light that I may read by them.

[Opens the letter and reads]

"Brutus, thou sleep’st. Awake, and see thyself.
Shall Rome, etc.? Speak, strike, redress.”—
"Brutus, thou sleep’st. Awake!”
Such instigations have been often dropped
Where I have took them up.
"Shall Rome, etc.?” Thus must I piece it out:
Shall Rome stand under one man’s awe? What, Rome?
My ancestors did from the streets of Rome
The Tarquin drive when he was called a king.
"Speak, strike, redress!” Am I entreated
To speak and strike? O Rome, I make thee promise,
If the redress will follow, thou receivest
Thy full petition at the hand of Brutus!

What effect does the letter have on Brutus?

Brutus decides to warn Caesar that his life is in danger.
Brutus thinks that Cassius is committing treason against Rome.
Brutus decides to join the conspiracy to kill Caesar.
Brutus tells Lucius to block the door against the conspirators.