...to discover, to encourage and, most important of all, to challenge 23 gifted young people all over the world.
答案：(D) mathematically
mathematically gifted 意為「有數學天分的」：國際數學奧林匹亞的首要目標是發掘、鼓勵並挑戰全世界具數學天分的年輕人；destructively（破壞性地）、effectively（有效地）、mutually（互相地）語意都不合。
答對率 38%。
四個選項都是 -ly 結尾的副詞，你大概靠語感挑。關鍵是看它修飾的是哪個字：空格後面是 gifted（有天分的），所以要問「在哪方面有天分」——本篇談的是國際數學奧林匹亞，答案當然是 mathematically（在數學方面）。「副詞加形容詞的組合，先確認形容詞在講什麼，再挑能限定範圍的副詞。」
mathematically gifted（有數學天分的）、musically talented（有音樂才華的）、physically fit（體能好的）、financially independent（經濟獨立的）——都是「副詞＋形容詞」限定範圍的用法，寫作時很好用。
同句前面就寫著 With arduous but interesting math problems（透過艱難卻有趣的數學題目），整句都在講數學競賽，範圍再清楚不過。
mathematically gifted（有數學天分的）、musically talented（有音樂才華的）、physically fit（體能好的）、be gifted in（在…方面有天分）、foster friendly relations（培養友好關係）。
There are six international science Olympiads in the world. They are all organized with a simple intention—to 21 global understanding and mutual appreciation among young scientists in all countries. Each of the six science Olympiads 22 its specific aims.
The aims of the International Mathematical Olympiad (IMO), for example, are three-fold. With arduous but interesting math problems, the first aim of the IMO is to discover, to encourage and, most important of all, to challenge 23 gifted young people all over the world. Secondly, it is by participating in any IMO contest that young mathematicians of all countries can foster friendly 24.
Based upon its second aim, more international exchanges are encouraged and established. Any IMO contest brings not only young mathematicians together but also their instructors; 25, the IMO has its final aim to create opportunities for the exchange of information on math schedules and practice throughout the world.