For Krashen, fluent speaking is mainly:

1. Krashen says speaking in the target language does not itself result in acquisition. 2. Speaking can indirectly assist, but the ability to speak is not the cause of acquisition. 3. Instead, comprehensible output is the effect of acquisition built from comprehensible input. 4. So talking is not practising; it appears after input has done its work. 5. Spontaneous speech comes from the acquired system, not from learned rules alone. 6. Therefore fluent speech is the result of acquisition, not the cause of it. **Why the other options fail:** - The cause of acquisition reverses Krashen's order, since speech is the effect. - A product of rule drills is wrong because learned rules only monitor output. - Unrelated to input is wrong because acquisition depends entirely on comprehensible input. _Source: Wikipedia, "Input hypothesis", section "Corollaries of the input hypothesis" (revision 1380165607)_