Would you please speak a little ___(slowly)?

a little more slowly ,若可以填两个词的话.
a little ,much even ,a lot,far 后面都可跟形容词或副词的比较级

a little slower.如果只能填一个词的话。
或者a little more slowly ,若可以填两个词的话.

翻译做，你能说得慢点吗，我没明白