Indicate whether each of the following occurs mainly in G₁ phase (G), S phase (S), or G₂ phase (H) of the cell cycle. Your answer would be a four-letter string composed of letters G, S, and H only, e.g. HGSS.
( ) DNA helicase activation
( ) DNA helicase deposition on DNA at the replication origins
( ) ORC phosphorylation
( ) Licensing of replication origins