Answer: -
LD50 stands for median lethal dose. It is the dose required to kill half the members of a tested population after a specified test duration.
Thus lower the LD50 value, lower the amount required to kill half the number of people in a tested population.
Thus lower the LD50 value, more lethal it is. Thus 3% Hydrogen Peroxide having an oral LD50 of 900 mg/kg is more more hazardous to consume than Acetic Acid with an oral LD50 of 3310 mg/kg.