How many of the following statements are incorrect? (1) The gobar gas is a special type of biogas generated from the dung of cattle (2) A floating cover is placed over the slurry, which keeps on rising as the gas is produced in the tank due to the microbial activity (3) A typical biogas plant has two main outlets, one for biogas which is used by nearby houses and the other for spent which may be used as fertiliser (4) The technology of biogas production was developed in India mainly due to the efforts of IARI and KVIC