However, more than 1,000 tons are low-grade and hard to smelt.

然而其中1 000多吨是低品位难选冶金矿。

A low-grade resource is not necessarily a low-quality resource..

等级低的资源未必是质量低的资源。

Often, a low-grade fever is actually helping fight off an infection.

通常情况下，低烧实际上在帮助战胜感染。

Some talk of 6m barrels a day in the future, albeit much of it low-grade.

有些人预言将来原油的产量是每天六百捅，尽管许多都是低等级原油。

Outlined -- although the benign tumor, but potentially malignant or low-grade.

本肿瘤虽属良性，但具潜在恶性或低度恶性。