The phone was definitely being monitored, so Gao Guang had to carefully consider every single word before he spoke, to make sure there wouldn't be any issue.
But Gao Guang would rather be monitored than ask Ray for a cell phone.
"Hello, teacher, it's Miss Sara. May I ask if you are able to take the call?"
There was a small surprise, as it was Sara, not Otto, who answered the call.
Gao Guang wondered, had Otto and Sara's relationship progressed to the point where Sara could answer calls for him?
"Your teacher wants me to ask you why you are using a fixed line number to make this call."
Otto was still very cautious, Gao Guang thought for a moment and said, "Uh, I can't say that, the phone number and its source are confidential, so I can't tell you."
By saying he couldn't say, it actually implied he could; by declaring the phone number's source was secret, it indicated the call undoubtedly originated from a place with numerous regulations.