Now, the main challenge was to find the right material for printing clothes with. I mean the material you feed the printer with.

现在，主要的挑战是找到合适的材料来打印衣服，我指的是你放入打印机的材料。

youdao

The main challenge will be to reduce the price of access devices.

而主要的挑战则来自降低接入设备的价格。

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The main challenge facing such a regime would be the incentive for regulatory arbitrage.

这个制度设计需要面对的最大挑战监管套利。

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Several decades ago, many people considered rising population to be the main challenge facing humanity.

FORBES: Thomas Malthus: Wrong Yesterday, Right Today?

The main challenge is overcoming viscousity, which means that completely different engineering principles are involved.

CNN: Nanobots get to the heart of the matter

The main challenge is to ensure the healing agent is robust enough to survive the mixing process.

BBC: Key test for re-healable concrete