In Dungeon World, human clerics and wizards each get to pick a spell from the other caster class's spell list. Must the player choose a level 1 spell so they can actually use it, or can they choose a higher level spell and hope they live long enough to take advantage of it?
In the Dungeon World core book it does not expressly state a level restriction on the bonus spell for human clerics and wizards from the wizard or cleric spell lists. It does clearly state level restrictions on known spells in the specific write-ups for the Cleric and Wizard.
That said, it does state the character can cast(Cleric p92, Wizard p146) the spell and the implication I draw from that is that this Move is intended for immediate use in the game, so the spell should be of a level the character can know and prepare. This implication is reinforced in the description of the Wizard's spellbook (p146) which refers to spells of a level which can be cast when describing starting spells, and again when describing adding spells when increasing level.