38 The oldest child in a family often______ quickly, learning early to take responsibility for his/her siblings.
(A) coincides
(B) declares
(C) interacts
(D) matures

The oldest child in a family often mature  quickly, learning early to take responsibility for his/her siblings

一個家庭中最大的孩子經常快速成長，早早地學習為他/她的兄弟姐妹承擔責任

(A) coincides  k,oɪns'ɑɪd  (v.)巧合,重合,一致,符合

(B) declares  dɪkl'ɛr  (vt.)斷言,宣稱;宣佈,宣告,聲明;申報(vi.)聲明,表明

(C) interacts  ,ɪntɚ'ækt   (vi.)互相影響,交互作用幕間劇,幕間休息

(D) matures  mətʃ'ʊr  (a.)成熟的,到期的,充分考慮的(vt.)使成熟(vi.)成熟,到期

sibling s'ɪblɪŋ  兄弟,同屬

The oldest child in a family often matures quickly, learning early to take responsibility for his/her siblings. 

一個家庭中最大的孩子通常成熟地很快,會較早學習去承擔他/她兄弟姊妹的責任。

The oldest child in a family often maturesquickly,
learning early to take responsibility for his/her siblings.
家庭中最大的孩子通常成熟得很快，
很早就學會了對他/她的兄弟姐妹負責。

(1)    mature    
       成熟: like a adult

       He's very mature for his age.

       慎重的，經深思熟慮的

        Upon mature reflection, we find the accused guilty.

        a)       coincide巧合
                to be the same or similar

                If our schedules coincide, we'll go to Spain together.

        b)      declare                 聲明:express

                They declared their support for the proposal.

                申報

                Goods to declare.

        c)       interact相互作用
                to communicate with or react to

                It's interesting at parties to see how people interact socially.

(2)    siblings兄弟姊妹

        I have four siblings: three brothers and a sister.

參考來源：劍橋辭典 Cambridge Dictionary