Which trees stay green all years: maples, elms or fir trees?

译句：下列哪种树木常年保持绿色：枫树，榆树还是冷杉树？（答案附在文末）

stay /ste/ vt. & vi. 停留; 停止

[同义词]：remain

[反义词]：change, move, depart

[惯用语]：

stay calm 保持冷静

stay healthy 保持健康

stay alive 活着；仍然活着

stay out of 置身于……之外

stay up late 熬夜；睡得很晚

stay in 呆在家里；不外出

stay with 同…住在一起；把…坚持下去

[例句 ]：

• I stayed up really late last night.

我昨晚熬夜到很晚，

• Stay hungry, stay foolish.

求知若饥，虚怀若愚。

• Stay calm, don't lose your temper.

保持冷静，别发脾气。

maple /'mepl/ n. 枫树

[惯用语]：

maple syrup n. 枫蜜；糖枫汁

maple tree 枫树

red maple 红枫

[例句]：

• Maple syrup is made from the sap of maple trees.

枫蜜是由枫树的树液制成的。

• We are going to a valley to see red maple trees.

我们要去山谷看看红叶。

elm/ɛlm/ n. 榆树, 榆木；adj. 榆树的, 榆木的

[例句]：

• An elm is a type of large tall broad-leaved tree.

榆树是一种高大的阔叶树。

• There's an elm tree to the left of the house.

房子左边儿有一棵榆树。

fir /fɝ/ n. 冷杉树

[例句]：

• The birds built their nest in the small fir tree.

鸟在小冷杉树上搭巢。

• My father had brought a fir tree in from the garden for christmas.

我父亲从花园里拿了一棵冷杉进来做圣诞树。

答案： fir trees