Hey there! I'm happy to help!
I'm seeing five verbs here: leer, caer, destruir, construir, oír. Leer is to read, caer is to fall, destruir is to destroy, construir is to construct and oír is to hear. So, know that the correct answer is between cayeron and cayó because caer means to fall, which matches the meaning "to fall", which is in this sentence.
Cayeron translates as "they fell". Cayó translates as "he, she, it, or formal you". Since we know we are talking about a "he", the correct translation is cayó.
I hope that this helps! Have a wonderful day!