Answer:
"That withstands winter winds".
Step-by-step explanation:
Adjective clauses are those dependent clauses that works or are used to describe the noun in a sentence. They provide an extra detail to the noun, giving it more specific description for more information.
In the sentence given-
The tree that withstands winter winds is strengthened.
"the tree" is the noun/subject of which the whole sentence is based off.
Now, an independent clause is a clause that can be used alone and give a meaningful whole sentence of its own. Whereas a dependent clause is a clause or group of words that has to depend on the other words/ independent clause to be able to have a full meaningful sentence.
So, considering the adjective clause "that can withstand winter winds", the remaining sentences "the tree is strengthened' is a full meaningful sentence. But added with the adjective clause, the sentence is given more 'color' or 'body', more description.
Thus, the adjective clause in the sentence is
"that withstands winter winds".