Which pair of animals fits the description: breathing through lungs, having gills when young and lungs later, moist skin without scales, and laying eggs?

• i) Breathe through the lungs (as adults).
• ii) Have gills when young and later lungs for breathing (metamorphosis).
• iii) Body covered with moist skin without scales.
• iv) Lays eggs. These characteristics collectively describe amphibians.

• A. Newt and salamander: Both are amphibians. They fit all the described characteristics.
• B. Lizard and tortoise: Both are reptiles. They breathe with lungs throughout their lives, have dry, scaly skin, and do not have gills when young.
• C. Toad and tortoise: A toad is an amphibian, but a tortoise is a reptile. This pair does not fit.
• D. Frog and tilapia: A frog is an amphibian, but a tilapia is a fish. Fish breathe with gills throughout their lives and have scales. This pair does not fit.

Only newts and salamanders (Option A) are amphibians and possess all the listed characteristics.

The final answer is $\boxed{\text{A. Newt and salamander}}$

17. The question asks to identify a common disease of the breathing system.

• A. Asthma: This is a chronic respiratory disease that causes inflammation and narrowing of the airways, making it difficult to breathe. It directly affects the breathing system.
• B. Malaria: This is an infectious disease caused by parasites transmitted through mosquito bites, primarily affecting red blood cells and various organs, but not primarily the breathing system.
• C. Cholera: This is a bacterial infection of the small intestine, causing severe diarrhea and dehydration. It affects the digestive system.
• D. Ringworm: This is a common fungal infection of the skin. It affects the skin.

Based on the analysis, Asthma is a disease of the breathing system.

The final answer is $\boxed{\text{A. Asthma}}$