I think so.

I tink so.
  • (1) そう思います。Sou omoimasu. = I think so. --- ○
  • (2) そうだと思います。Sou da to omoimasu. = I think that's right. (lit. I think that is so.) --- ○
  • (3) そうと思います。Sou to omoimasu. = I think so. --- ×△
  • ○ = correct, △ = so-so, × = incorrect