這一定是我。

It has to be me.

Source: Tatoeba

Sentence Composition

=1 這 zhè
  1. (pronoun) this; these
  2. (bound form) this; the (followed by a noun)
  3. (bound form) this; these (followed by a classifier) (in this sense, commonly pr. zhèi, esp. in Beijing)
=1 這 zhèi (coll.) this
2 一定 yīdìng
  1. surely
  2. certainly
  3. necessarily
  4. fixed
  5. a certain (extent etc)
  6. given
  7. particular
  8. must
=3 是 shì
  1. to be (followed by substantives only)
  2. correct; right; true
  3. (respectful acknowledgement of a command) very well
  4. (adverb for emphatic assertion)
=3 是 shì variant of 是 shì
4 我 wǒ
  1. I
  2. me
  3. my