The amount of needed to protect a particular path in a project is less than the sum of the required to protect the individual activities making up the path.

The amount of safety time needed to protect a particular path in a project is less than the sum of the safety times required to protect the individual activities making up the path

See explanation below

Explanation:

Is important to remember two important concepts:

Safety Stock

Defined as an "additional quantity of an item held in inventory in order to reduce the risk that the item will be out of stock. Safety stock helps in case the sales of an item are greater than planned or in case that the supplier would be unable to deliver additional units at the expected time".

Safety Lead Time

Defined as a form to represent your safety stock as a number of days, months, years  of the demand. and is very useful in order to determine how many time we can have supply the demand required

Based on these defintions the best answer for the phrase proposed would be:

The amount of safety time needed to protect a particular path in a project is less than the sum of the safety times required to protect the individual activities making up the path

answer(d) all of the choices are correct;