From the four answers provided below, please select the MOST CORRECT option that best aligns to the query posed in Question $1$ within the Topic $4$ lecture. Please remember that the terms have been replace with $\text{'}$X$\text{'}$ and $\text{'}$Y$\text{'}.$ Therefore, ensure that you have the meanings of the $\text{'}$X$\text{'}$ and $\text{'}$Y$\text{'}$ codes before you start this question. Hint: Read the options carefully, as there is only one fully correct option.

Question $1$Select one:

$1.$

$\text{'}$Xs$\text{'}$ refer to significant events that normally have no duration, cost or resource requirements associated with them. $\text{'}$Ys$\text{'}$ are elements of work normally found in a WBS$,$ which have an expected duration, cost and resource requirements.

$2.$

$\text{'}$Xs$\text{'}$ by definition have no duration, but must have a logical relationship with $\text{'}$Ys$\text{'}.$ These relationships may include the provision of leads and lags. Alternately, $\text{'}$Ys$\text{'}$ must have a duration and resource allocations, so they can be applied to coordinate the Xs$.$

$3.$

$\text{'}$Xs$\text{'}$ must have predecessors and successors, but must not be aligned through leads or lags. Alternately, $\text{'}$Ys$\text{'}$ must always have leads and lags, as well as having a clear duration and resource requirements.

$4.$

$\text{'}$Xs$\text{'}$ are elements of work normally found in a WBS$,$ which have an expected duration, cost and resource requirements. $\text{'}$Ys$\text{'}$ refer to significant events that normally have no duration, cost or resource requirements associated with them.