Gray's early music was in a contemporary folk-rock, singer-songwriter mode; his primary instrument was acoustic guitar, with occasional piano.

Gray早期的音乐类型属于当代摇滚民谣并且是一个唱作人。他早期使用的乐器是原声吉他，偶尔使用钢琴。

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Keratometry - a keratometer is the primary instrument used to measure the curvature of the cornea.

角膜曲率检测——角膜曲率计是用来检测角膜曲率的仪器。

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The difficulty lies on keeping the amplitude in a proper range to activate the primary instrument, neither too high nor too low.

驱动设计的难点在于必须保持激振信号幅度在合适的范围内，过大过小都不能驱动一次仪表正常工作。

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In the early '90s, Amos earned notoriety for being one of the few up-and-coming female musicians to use piano as a primary instrument.

NPR: Tori Amos: From 'Sin' To Holiday Joy

This implies that a creditors primary concern is not the absolute safety of a bond or other credit instrument, but its relative safety.

FORBES: Inverse Moral Hazard: A Slaughter Rule For Finance