To our surprise, the festival this year draws three times                 .

a larger audience as last year’s did

as large an audience as did last year’s

larger as an audience as last year’s did

an audience large as did last year’s

考查倍数表达固定句型。句意：令我们吃惊的是，今年的电影节吸引了去年三倍的观众。倍数表达法有：“... times + 形容词/副词的比较级 + than ...”，“... times + as + 形容词/副词的原级 + as ...”，以及 “... times + the + 名词 (如：size，height，weight，length，width等) + of ...”。“... times as ... as ...” 意为 “……是……的……倍”，其中第一个as是副词，用以修饰后面的原级形容词或副词，第二个as是连词，用以引导比较状语从句，常有省略现象；本题中第一个as后用原级形容词large，第二个as后引导比较状语从句last year’s festival did，省略名词festival并使用了倒装。故选B。