During our stay in Hainan last year,we visited a small islan

答案为A;whose .
whose name实际就是： the name of the small island.
all of us have forgottn whose name(=the name of the small island)
希望对你有所帮助.
再问： 为什么不选C？
再答： 记住：whose +n. =the +n.+of which/whom = of which/whom +the +n. 如果选C的话，应该在name 前加上the。即：of which the name 明白了吗？