Question

Употребите инфинитив с частицей to или без нее:

Please let me (to know) your decision as soon as possible.
It's better (to be) sure than sorry.
He heard a cock (to crow) in a neighboring village.
We know all bodies (to consist) of atoms.

Answer 1

let me know to becrow consist

Answer 2

Please let me know your decision as soon as possible.
It's better to be sure than sorry.
He heard a cock crow in a neighbouring village.
We know (that) all bodies consist of atoms (Если рассматривать как сложноподчиненное предложение с придаточным "all bodies consist of atoms.) 
или
We know all bodies to consist of atoms (Если рассматривать как предложение с Complex object. Однако стоит сказать, что в языковой практике подобного рода сочетание наблюдается редко: более распространена конструкция to know smb + to be, и зачастую употребление глагола to know в предложениях с Complex object предполагает сочетание именно с глаголом to be. Например: "Everybody knows him to be a man of honour".)