How should i prepare for Hortonworks developer certificate HDPCD spark, what is the version of spark actually

[#1]

What is the version of spark in hdpcd spark certification exam.

My concern is that most of the documentation is available as per spark 2.x

[#2]

From Hortonworks itself, as of 9/3/18:

The exam has the following versions: • HDP 2.4.0 • Spark 1.6 • Scala 2.10.5 • Python 2.7.6 (pyspark)

In terms of how best to study for the exam, the following link provides the only real practice test with solutions that I've found to date: https://shoptly.com/sparkstudyguide