Why did europeans want access to china and japan?

The main reason why Europeans were interested in access to China and Japan was because they were looking for new markets for trade. While trade in Europe was successful, and Europeans traded with much of the world, the Far East represented an opportunity to access an untapped market. However, these were extremely closed societies, and when they eventually engaged in discussions, China and Japan had little interest in trading with Europe, as they  thought of them as less developed and did not see how they could benefit from trading with them.

the answer your looking for is c. : )