فَبِأَىِّ ءَالَآءِ رَبِّكُمَا تُكَذِّبَانِ
Fabi ayyi aalaaa'i Rabbikumaa tukazzibaan.
So which of your Lord's blessings will the two of you deny?
This one falls after a single word, afnān, which the tradition read two ways: as branches spreading over the garden, and as varieties, gardens of many kinds. Either reading makes the question that follows land on foliage, of all things. Ālāʾ covers favor and also displayed power, which is why the same refrain can follow a description of fire earlier in the surah and shade here.