22. In TGF-b pathway, R-Smads are activated by phosphorylation and form complex with Smad4, then this complex enter nucleus. Which of the following statement is not correct? (A) If the oligomerization domain on R-Smads is deleted, the TGF-b signaling is more active. (B) If the NLS (nuclear localization signal) on Smads is lost, TGF-b signaling will be reduced. (C) ubiquitination for protein degradation on R-Smads will promote signaling (D) over-expression phosphatase for R-Smads will reduce signaling