A crane was already unloading crates and pallets.是什么意思？

A crane was already unloading crates and pallets.

起重机已经开始卸载木箱和托盘了。

crane

n. 吊车，起重机，鹤；vt.& vi. 伸长，探头；vi. 迟疑，踌躇；

例句
A crane was already unloading crates and pallets.
起重机已经开始卸载木箱和托盘了。

was

v. 用来表示某人或某物即主语本身，用来表示某人或某物属于某一群体或有某种性质（ be的过去式 ），在，存在，不受干扰；

例句
There was a terrible sadness in her eyes...
她眼神中流露出深深的悲伤。

already

adv. 早已，已经，先前；

例句
He has already voted by absentee ballot...
他已进行了缺席投票。

unloading

n. 卸载；v. 从…卸下货物( unload的现在分词 )，摆脱，拆掉，脱手；

例句
A crane was already unloading crates and pallets.
起重机已经开始卸载木箱和托盘了。

crates

n. 板条箱，柳条箱( crate的名词复数 )，装货箱，一箱（之量），破旧的汽车[飞机]；

例句
A crane was already unloading crates and pallets.
起重机已经开始卸载木箱和托盘了。

and

conj. 和，与，而且，于是，然后，因此；

例句
I spend a lot on expensive jewelry and clothing...
我花很多钱购买昂贵的首饰和衣服。

pallets

n. 托盘( pallet的名词复数 )，平台，运货板，草垫子；

例句
The warehouse will hold more than 90,000 pallets storing 30 million Easter eggs.
那间仓库将用9万多个货盘装3,000万只复活节彩蛋。