
$$h d n s\ T_{f_{5}},\,C$$
$$m/n$$
$$m/n$$

## 4. A Causal Hypothesis 4.1 Backbone Fragility : Motivation

B

$${\boldsymbol{C}}$$
B QB W SAT C' Q B C - B C - B C B C Q B W SAT C C - B Q B C C - B TB E QB C - B hdns TB, C hdns T B , C W SAT
$$C-B$$
$${\boldsymbol{C}}$$
$$Q_{B}$$
$$\begin{array}{c}{{b a\,c k b o n e\,\mbox{-}f r a\,g i l e}}\\ {{b a\,c k b o n e\,\mbox{-}r o\,b u s\,t}}\end{array}$$
$$C_{}^{*}$$
$$\begin{array}{c}{{l}}\\ {{l}}\\ {{l}}\end{array}$$
$$\begin{array}{c c c}{{l}}&{{}}&{{}}&{{C}}\end{array}$$
