So, basically, withholding information is not the same thing as lying, but depending on the situation, you will have to decide whether it is better to withhold the information or not.
HCH may refer to: Hampton Court House, an independent school in Surrey, UK. Hexachlorocyclohexane, a group of chemical compounds. Holmes Chapel railway station (National Rail station code), in Cheshire, England.
MCH: Abbreviation for mean cell hemoglobin, which is the average amount of hemoglobin in the average red cell. The MCH is a calculated value derived from the measurement of hemoglobin and the red cell count.