Об­ра­зуй­те от слова EXTEND од­но­ко­рен­ное слово так, чтобы оно грам­ма­ти­че­ски и лек­си­че­ски со­от­вет­ство­ва­ло со­дер­жа­нию тек­ста.

Even if you have an acceptable grasp of the English language, with good grammar and an __________________ vocabulary, native English speakers may find you very difficult to understand you if you don't work on your pronunciation.