Sentence:  Conjunctions of I and II [Io and Europa] occur when they are near perigee and <WSD>apogee</WSD> respectively; conjunctions of II and III [Europa and Ganymede] occur when II [Europa] is near perigee. 
Meaning of the word marked with <WSD> tags:  The point, in an orbit about any planet, that is farthest from the planet: the apoapsis of any satellite.