Parallel execution sequence Which statement is correct about the parallel executions plan?

A. The CUSTOMERS and SALES tables are scanned simultaneously in parallel and then joined in parallel.
B. First, the CUSTOMERS table is scanned in parallel, then the SALES table is scanned in parallel, and then they are joined serially.
C. First, the SALES table is scanned in parallel, then the CUSTOMERS table us scanned in parallel, and then they are joined in parallel.
D. The CUSTOMERS and SALES tables are scanned simultaneously in parallel and thenjoined serially.
E. First, the CUSTOMERS table is scanned in parallel, then the SALES table us scanned in parallel, and then they are joined in parallel.

I think E is correct but the correct answer is A. Why?
B, D incorrect:

The join is performed in parallel, there is only 1 serial operation on the picture, only one parallel->serial (P->S) transition, and that is when the query coordinator collects the results. 

A (, D) incorrect: 

Parallel SQL uses the producer-consumer model. One set reads the table, the other set builds/probes the hash table, they do not read seperate tables simultaneously.

C incorrect:

There is only 1 DFO (:TQ1), the order of execution can be easily recognized by the order of virtual tables or the table queues (:TQ1000x). This is not necessarily true for multiple DFOs, but it is inside 1 DFO. :TQ10000 comes before :TQ10001, but :TQ10000 does not necessarily come before :TQ20000. Read more about this:

https://jonathanlewis.wordpress.com/2015/12/21/parallel-plans-2/

So the first table to be read is CUSTOMER, not SALES.

E correct:

Well, this is how it works, but that is not a real explanation. Easier to prove the other options wrong.