_____ gave the terms acquisition, observation, natural, input, dominant hypothesis in the theory of Second Language learning.

The correct answer is Stephen Krashen.

Stephen Krashen, a renowned linguist and educational researcher, introduced the Input Hypothesis model in the late 1970s and 1980s, which is one of the most influential theories in Second Language Acquisition (SLA).

Krashen's theory of Second Language Acquisition consists of five main hypotheses:
1. The Acquisition-Learning Hypothesis: Distinguishes between "acquisition" (a subconscious, natural process similar to how children learn their first language) and "learning" (a conscious, formal process of learning rules).
2. The Monitor Hypothesis: Explains how conscious learning acts as a monitor or editor, correcting or polishing the language produced by the acquired system.
3. The Natural Order Hypothesis: Suggests that the acquisition of grammatical structures follows a predictable, "natural" order regardless of the learner's age or background.
4. The Input Hypothesis: Postulates that language is acquired when learners receive "comprehensible input" that is slightly beyond their current level of competence (often represented as $i+1$).
5. The Affective Filter Hypothesis: Proposes that emotional variables (such as anxiety, self-confidence, and motivation) can act as an invisible barrier (filter) that prevents input from reaching the language acquisition device in the brain.

Therefore, the terms acquisition, observation (in the context of monitoring), natural, input, and the dominant hypotheses in second language learning are attributed to Stephen Krashen.