A packing box has a bottom surface formed double by folding flaps 11 through 14 extending downward from respective four side surfaces 1 through 4 such that mutually-opposing flaps are folded in a pair. The second part has an inner surface forming in the inner position with the first-part inner surface a cavity open outwardly in the direction. The load-and-unload cup may be configured to move to and from the wafer carriers in a linear reciprocating manner. The sectors of the optical disc are verified to determine whether any one of the unverified sectors having user data is defective. This new and distinct variety has shown to be uniform and stable in the resulting generations from asexual propagation. A silicon etching liquid which is an alkaline aqueous solution containing an alkali metal hydroxide, hydroxylamine and an inorganic carbonate compound and having a pH of 12 or more and which is able to anisotropically dissolve monocrystalline silicon therein, and an etching method of silicon using this etching liquid are provided.