sir,our science teacher explained to us that liquids can not be compressed.
but in this session you explained that liquids are slightly compressible.
how?

Dear Student,

There are two types of fluids in nature one is newtonian and other is non-newtonian fluids, newtonian can be compressed while the other cannot be compressed water comes under newtonian fluid hence it can be compressed while oil (crude) comes under non-newtonian hence it can be compressed.

If water is not able to compress then there will be no such steam engine exists and other mechanical existence, hence the answer is big YES for water compression but only high pressure is needed to deal with it.

Regards.