Find the part of the given sentence that has an error in it.
I'm unable to contact my friend, who deceived me when I was more weaker.

Option (a) contains an error.
Explanation:
1. "Weaker" is already a comparative adjective, and adding "more" is grammatically incorrect.
2. The correct form is simply "weaker" without "more."
3. Comparatives like "weaker" do not require intensifiers like "more."
Hindi Explanation: "Weaker" पहले से ही तुलनात्मक रूप है। इसे "more" के साथ उपयोग करना गलत है। सही वाक्य होगा: "when I was weaker."
Corrected Sentence: I'm unable to contact my friend, who deceived me when I was weaker.