Chinese Test: What on earth shall I wear?

Beginner Level 初级 (chūjí)
Conversation:
Mary is going to a dance party without having any idea of what she wants to wear. So she asks her friend Anne for some advice.
Qīn, nǐ juéde wǒ chuān nǎ jiàn bǐjiào hǎo ne?
Mary: 亲，你觉得 我 穿 哪 件 比较 好 呢？
Zhè jiàn bú cuò.
Anne: 这 件 不 错。
Kě wǒ juéde yánsè bú tài hǎo. Zhè jiàn zěnmeyàng?
Mary: 可我 觉得 颜色 不 太 好。这 件 怎么样？
Kěyǐ, dàn gǎnjué bú tài zhèngshì.
Anne: 可以，但 感觉 不 太 正式。
Ài, wǒ gāi chuān shénme ya? Zhēn shì tóu dà a!
Mary: 哎，我该 穿 什么 呀？真 是 头 大啊！
In this dialogue, what does “头大 (tóu dà)” mean?
A. a big head
B. brain fart
C. distraught
See Answer at
http://resources.echineselearning.com/minitestanswers/minitestanswers-chinese-763.html?ecl=ptEEEEEEpg1272903