Question

question 1
what does the data link layer add to a layer 3 packet to create a frame? (choose two.)
flags
sequence number
header
trailer
question 2
what is the function of the last field in a data link layer frame?
to determine whether the frame experienced transmission errors
to identify special flow control services such as quality of service (qos)
to identify the beginning and end limits of the frame
to identify the layer 3 protocol in the data field

Explanation:

For Question 1: The data - link layer adds a header and a trailer to a Layer 3 packet to create a frame. Flags are not the main elements added in this context and sequence numbers are more relevant in transport - layer functions.
For Question 2: The last field in a data - link layer frame is usually a trailer which contains a Frame Check Sequence (FCS) used to determine if there were transmission errors. It is not used for identifying QoS, frame limits, or Layer 3 protocol in the data field.

Answer:

Question 1: C. Header, D. Trailer
Question 2: A. To determine whether the frame experienced transmission errors