It is one of the key challenges in natural language understanding, and has drawn increasing attention in recent years (Levesque et al., 2011;Roemmele et al., 2011;Zhang et al., 2017;Rashkin et al., 2018a,b;Zellers et al., 2018;Trinh and Le, 2018).
due to the lack of labeled training data or comprehensive hand-crafted knowledge bases, commonsense reasoning tasks such as Winograd Schema Challenge (Levesque et al., 2011) are still far from being solved.