The correct answer is: B. Thailand and Cambodia
Buddhism first went to China during the reign of Emperor Wu of Han (141-87 BCE). It was introduced by the Indian monk Kashyapa Matanga, who was invited to China by the emperor. Buddhism quickly spread throughout China, and by the 3rd century CE, it had become the dominant religion in the country.
From China, Buddhism spread to other parts of Asia, including Thailand and Cambodia. The first Buddhist missionaries to Thailand arrived in the 3rd century CE, and the religion quickly became popular among the Thai people. Buddhism was also introduced to Cambodia in the 3rd century CE, and it has been a major religion in the country ever since.
The other options are incorrect because they do not accurately reflect the spread of Buddhism from China. Option A, Burma and Tibet, is incorrect because Buddhism did not reach Burma until the 6th century CE, and it did not reach Tibet until the 8th century CE. Option C, Korea and Japan, is incorrect because Buddhism did not reach Korea until the 4th century CE, and it did not reach Japan until the 6th century CE. Option D, Indonesia and Vietnam, is incorrect because Buddhism did not reach Indonesia until the 7th century CE, and it did not reach Vietnam until the 10th century CE.