这些早期的实验是现代计算机技术的先驱。

These early experiments were the ___precursors of modern computer technology.

这种化学物质是制造塑料的重要前体。

This chemical is an important ___precursor for making plastic.

频繁头痛可能是偏头痛的前兆。

Frequent headaches can be ___precursors to migraines.