Some of the emails had the subject line, "Think Twice." They were sent from a spoofed email address. The sender claimed to have had an associate plant a small bomb in the recipient's building and said the only way to stop him from setting it off was by making an online payment of $20,000 in bitcoin.

Based on that paragraph can we conclude that this sentence is true?
The sender did not claim to be acting alone

Pick from:
[a]. Yes.
[b]. It's impossible to say.
[c]. No.
[a].