Answer:   SEQUENCE - You use the SEQUENCE step to build a set of steps that you want to treat as a group. Steps in a group are executed in order, one after another. By default, all steps in a flow service, except for children of a BRANCH step, are executed as though they were members of an implicit SEQUENCE step (that is, they execute in order, one after another). However, there are times when it is useful to explicitly group a set of steps.

BRANCH - The BRANCH step allows you to conditionally execute a step based on the value of a variable at run time. For example, you might use a BRANCH step to process a purchase order one way if the PaymentType value is “CREDIT CARD” and another way if it is “CORP ACCT”.
SEQUENCE - You use the SEQUENCE step to build a set of steps that you want to treat as a group. Steps in a group are executed in order, one after another. By default, all steps in a flow service, except for children of a BRANCH step, are executed as though they were members of an implicit SEQUENCE step (that is, they execute in order, one after another). However, there are times when it is useful to explicitly group a set of steps.

BRANCH - The BRANCH step allows you to conditionally execute a step based on the value of a variable at run time.