The correct options are
A Dams can be constructed only in limited areas.
B Large areas of land get submerged in water when dams are constructed.
C Submerged vegetation rots under anaerobic conditions and produces methane, a greenhouse gas.
Some disadvantages are:
1. Dams store water from water resources like rivers, which is limited to some areas where all the required parameters to construct a dam will be satisfied.
2. As large areas get submerged in water there is a huge loss of flora and fauna of that area. People and animals living there need to be relocated to a different place.
3. The biomass submerged in water slowly rots and produces methane which causes the greenhouse effect and contributes to global warming.
4. The high cost of construction.
5. Leakage in dams can cause flooding of entire valleys and scenic areas. Many times these accidents are hazardous and cause great loss of life and property.