On number 3, that behavior is exactly what I would expect. Not sure what other logical behavior you would propose...

The other options don't make sense:

"A) Aligned horizontally with the first two, but after both of them?"

Floats are taken out of the normal flow so they will be pulled as far to the side as possible until they reach another floated element or the edge of the BFC.

"B) On the row after the first two, on the far left side?" "C) On the row after the first two, on the far right side?"

They are floated elements in the same BFC, if they fit on the same line, they will. Unless you clear them. Pretty simple stuff.