Image forming apparatus and cartridge

An image forming apparatus for forming an image on a recording material, comprising:

• a cartridge supporting member including a plurality of mounting portions in which each including a developer accommodating portion for accommodating a developer for developing electrostatic latent image formed on a photosensitive member a plurality of cartridges is detachably mountable, said cartridge supporting member being movable between an inside position inside a main assembly of said image forming apparatus and an outside position outside the main assembly;
• a plurality of preventing members provided movably in the main assembly, wherein each preventing member is movable, when said cartridge supporting member is moved from the outside position to the inside position, between a first position in which each preventing member prevents movement of said cartridge supporting member from the outside position to the inside position by contacting said cartridge supporting member and a second position, retracted from the first position, in which each preventing member permits the movement of said cartridge supporting member;
• a plurality of releasing means provided movably in said cartridge supporting member, wherein each releasing means is movable between a releasing position in which each releasing means positions an associated preventing member at the second position in contact with the associated preventing member only when an associated cartridge is mounted in an associated mounting portion and a non-releasing position in which each releasing means positions the associated preventing member at the first position in non-contact with the associated preventing member when the associated cartridge is unmounted in the associated mounting portion or when the cartridge different from the associated cartridge is mounted in the associated mounting portion.