An 
linear collider has been emphasized [8] to complement a pp
collider under the current schedule: that the LHC will have 9.3TeV collisions in 2004
then full 14TeV in 2007. [7]
The most relevant complementarity is that a 300GeV collider can certainly find
a light Higgs boson of 
, the ultimate performance that the LHC needs to discover, since
the Higgs boson is a key concerning electroweak symmetry breaking. For full
complementarity to a pp collider, collider should operate at the optimum
center-of-mass energies with high beam polarizations for detailed studies of top quark,
Higgs boson and particles, as mentioned in the previous section. [3]
Since the both colliders have many overlapping regions, though concerning different
aspects, to explore new physics, even at a 500GeV linear collider, we should
also emphasize competition for simultaneous experiments. We have learned from
history that healthy competition has generally promoted high-energy physics programs in the
world, and has contributed to the understanding of fundamental physics.