how many labels does PE1 push onto data packets destined for PE2?

Refer to the Exhibit.

Customer A wants a Layer 3 VPN between their two sites. To support this, you purchase a carrier-of-carriers solution from ISP2. Referring to the topology in the exhibit, how many labels does PE1
push onto data packets destined for PE2?

A.
1

B.
2

C.
3

D.
4