Here are the phrasal verbs that have the same meaning as the underlined words:

21. **went to bed** - **C. take up** (although it doesn't mean exactly the same, it is a feasible choice in context, "take up" can imply starting to sleep).
22. **felt let down** - **C. put out** (this is the closest in meaning to disappointment).
23. **light up** - **D. smoke** (as it refers to starting to smoke a cigarette).
24. **make out** - **B. understand** (this fits as you need to comprehend or discern something).
25. **looking on** - **D. watching** (as it means to observe).
26. **looking for** - **B. finding out** (this captures the sense of searching for something).

If you need further clarification or additional context, let me know!