main bottom的用法和樣例：
例句
- The lithology and the weathering degree of the bed rocks are the main factors to determine their physical mechanical properties.
基岩的岩性和風化程度是決定其物理力學性質的王要因素。 - As a main method, seismic exploration can determine the depths of basement rocks and investigate the fault activity according to the extension of the fault in Quaternary layers.
作為一種主要手段，地震勘查能夠查明基岩埋深，根據基岩斷層向第四系地層內部的延伸可研究斷層的活動性。
