This study dealt with analysis of the study units in the textbook "Horizons" for 9th-grade students studying English in mixed ability classes. The study sought to examine the variety in the cognitive level represented by the WH-questions in the textbook according to Bloom's taxonomy. The study also attempted to examine the extent in which the WH-questions in the textbook emphasize high-level thinking, and whether the textbook aided students in developing cognitive skills. The study attempted to answer the following question: To what extent are the WH-questions in the six levels of the cognitive domain varied or frequent in the textbook of "Horizons"? Content analysis was conducted for the six study units in the textbook "Horizons". The researcher chose the question as the unit for analysis for his research. The question is defined as a WH-question--in other words--a question beginning with a "wh"-word and ending with a question mark. The questions were collected, listed, and analyzed according to Bloom's Taxonomy: low order thinking skills: knowledge, comprehension, and application, and high order thinking skills: analysis, synthesis, and evaluation. The researcher then calculated the percentage and frequencies in which each level of cognition appeared for each separate unit and for all six units combined. The results indicated that the research tools used by the two analysts were valid and reliable. The results showed that 244 questions emphasized levels of cognition representing lower order thinking skills, while only 137 questions emphasized the three higher order thinking skills. The questions in the "Horizons" textbook place a great deal of emphasis upon comprehension, which is one of the lower order thinking skills. Additional studies are recommended in the area of content analysis of English instruction textbooks intended for various age levels in the Arab Sector. Such studies would shed light upon the role of textbooks in developing cognitive skills among Arab students.