马戏团的杂技演员在没有任何保护措施的情况下，在高空钢丝上完成了后空翻。

The circus acrobat performed a backflip on the ___high-wire without any safety harness.

在股市中投资就像走钢丝，需要极高的技巧和谨慎。

Investing in the stock market is like walking a ___high-wire, requiring great skill and caution.