太阳能是煤炭能源的一个可行替代方案。

Solar energy is a ___viable alternative to coal power.

一个项目要成功，需要在财务上可行。

For a project to succeed, it needs to be financially ___viable.

这是一个需要合理答案和可行解决方案的问题。

This is a question that demands reasonable answers and ___viable solutions.