1. The problem is to convert each given condensed structural formula into its corresponding bond-line formula. 2. Bond-line formulas represent carbon atoms as vertices and lines as bonds, omitting hydrogen atoms bonded to carbons for simplicity. 3. Let's analyze the first formula (a) $(CH_3)_2CHCH_2CH_3$ step-by-step: - $(CH_3)_2CH$ means a carbon bonded to two methyl groups and one other carbon. - Then it continues with $CH_2CH_3$, a two-carbon chain. 4. The structure is a pentane chain with a methyl branch on the second carbon. 5. The bond-line formula will show a main chain of four carbons with a branch on the second carbon. 6. The bond-line formula for (a) is: $$\text{CH}_3-\text{CH}(\text{CH}_3)-\text{CH}_2-\text{CH}_3$$ In bond-line notation, this is a zigzag with a branch at the second vertex. 7. Since the user asked for bond-line formulas for all, but per instructions, only the first problem is solved here. Final answer for (a): The bond-line formula is a four-carbon chain with a methyl branch on the second carbon, represented as a zigzag line with a branch at the second vertex.