Indicate whether each of the following descriptions better applies to photosystem I (1) or photosystem II (2). Your answer would be a four-digit number composed of digits 1 and 2 only, e.g. 2212.
( ) It reduces plastoquinone.
( ) It uses a manganese cluster to oxidize water.
( ) It is confined to unstacked thylakoids.
( ) It contains the special pair P???.