The correct answer is option 'A', which states that warm temperate climates extend from 30-50 latitude. Let's break down this answer and explain it in detail:

1. Introduction to warm temperate climates:
- Warm temperate climates are characterized by mild winters and hot summers.
- These climates are located between the subtropical and cool temperate climates.

2. Latitude and climate zones:
- Latitude plays a significant role in determining the climate zones on Earth.
- As we move away from the equator towards the poles, the climate generally becomes cooler.

3. Explanation of the given options:
a) 30-50 latitude:
- The correct answer is option 'A', which states that warm temperate climates extend from 30-50 latitude.
- This means that the regions between 30 and 50 degrees latitude, both in the Northern and Southern Hemispheres, experience warm temperate climates.
- Examples of countries that fall within this latitude range and have warm temperate climates include parts of the United States, Spain, Italy, Australia, and Argentina.

b) 40-50 latitude:
- Option 'B' states that warm temperate climates extend from 40-50 latitude.
- This range is slightly higher than the correct answer, and it includes regions that are closer to the cool temperate climates.
- While some areas within this range may still experience warm temperate climates, it is not the most accurate option.

c) 35-40 latitude:
- Option 'C' states that warm temperate climates extend from 35-40 latitude.
- This range is even lower than the correct answer and falls within the subtropical climate zone.
- While some regions within this range may experience warm temperate climates, it is not a comprehensive representation of all warm temperate regions.

d) 40-50 latitude:
- Option 'D' states that warm temperate climates extend from 45-50 latitude.
- This range is the highest among all the given options and includes regions that are closer to the cool temperate and even subarctic climates.
- These regions generally do not fall within the warm temperate climate zone.

4. Conclusion:
- Based on the explanation above, option 'A' is the most accurate answer as it correctly identifies the latitude range (30-50) where warm temperate climates are found.