The book answer and the video answer both state: you need to know that the four-membered ring in penicillin derivatives is an electrophile… . Neither state how this is known.
What’s the thought process for working through this question? Do you have to ‘just know’ that carbonyls are electrophiles? Do you look at the molecule (p131) and start scanning for atoms with free lone-pairs, then assume it’s a nucleophilic attack and begin looking for nucleophiles?