In Type IIA/IIB string theory we can have various fluxes, such as the 3-form H-flux, and the various Ramond-Ramond fluxes in even/odd dimensions.
In 11D SUGRA, however, the field content seems to only contain the graviton, gravitino, and 4-form flux F. Why can't we have fluxes of other dimensions in 11D SUGRA?