  Major flares and coronal mass ejections (CMEs) tend to originate from the
compact polarity inversion lines (PILs) in the solar active regions (ARs).
Recently, a scenario named as "collisional shearing" is proposed by
\citet{Chintzoglou_2019} to explain the phenomenon, which suggests that the
collision between different emerging bipoles is able to form the compact PIL,
driving the shearing and flux cancellation that are responsible to the
subsequent large activities. In this work, through tracking the evolution of 19
emerging ARs from their birth until they produce the first major flares or
CMEs, we investigated the source PILs of the activities, i.e., the active PILs,
to explore the generality of "collisional shearing". We find that none of the
active PILs is the self PIL (sPIL) of a single bipole. We further find that 11
eruptions originate from the collisional PILs (cPILs) formed due to the
collision between different bipoles, 6 from the conjoined systems of sPIL and
cPIL, and 2 from the conjoined systems of sPIL and ePIL (external PIL between
the AR and the nearby preexisting polarities). Collision accompanied by
shearing and flux cancellation is found developing at all PILs prior to the
eruptions, with $84\%$ (16/19) cases having collisional length longer than
18~Mm. Moreover, we find that the magnitude of the flares is positively
correlated with the collisional length of the active PILs, indicating that the
intenser activities tend to originate from the PILs with severer collision. The
results suggest that the "collisional shearing", i.e., bipole-bipole
interaction during the flux emergence is a common process in driving the major
activities in emerging ARs.
