From the point of view of developers and users, which of the following best summarises key features introduced in iOS 9?

Introduction / Context:
Each major iOS release introduces new features for both end users and developers. iOS 9 focused on productivity, intelligence, and performance improvements, especially on the iPad. Knowing which features belong to which version can be useful in interviews about mobile development history or when maintaining legacy apps. This question asks you to identify the option that correctly summarises significant additions in iOS 9.

Given Data / Assumptions:

• iOS 9 followed iOS 8 and preceded later versions such as iOS 10.
• Apple emphasised multitasking enhancements for iPad, improvements to Siri, and system level optimisations.
• Earlier versions like iOS 2 introduced the App Store, and later versions added features not present in iOS 9.
• The options mix correct features with incorrect or unrealistic statements.

Concept / Approach:
The key user facing features of iOS 9 included split screen and slide over multitasking on supported iPads, allowing two apps to run side by side or in a small overlay. Siri became more proactive, offering suggestions based on usage patterns and context. The Notes app received major enhancements such as checklists and drawing tools. Apple Maps gained transit directions in selected cities. Under the hood, iOS 9 brought performance improvements, better battery life, and app thinning for more efficient storage usage. Comparing these known features to the options helps you select the correct summary.

Step-by-Step Solution:
Step 1: Recall that split view multitasking, slide over, and picture in picture were heavily advertised iPad features in iOS 9. Step 2: Remember that Proactive Siri and search enhancements allowed the system to suggest contacts, apps, and news before the user typed. Step 3: Note that Apple Maps transit directions and an improved Notes app were also highlighted in the release. Step 4: Compare this set of features with option a, which lists these elements and mentions performance and battery improvements. Step 5: Recognise that other options either describe much earlier milestones or unrealistic changes that never occurred.

Verification / Alternative check:
If you look at Apple press materials or remember the keynote for iOS 9, the focus was clearly on iPad multitasking, Proactive assistance, and system refinements. Features such as the original App Store or the introduction of copy and paste date back to very early iOS versions, not iOS 9. Options mentioning removal of multitasking or touch are inconsistent with Apple emphasis on richer multitasking and touch first interaction.

Why Other Options Are Wrong:
Option b attributes the original App Store and copy and paste introduction to iOS 9, but those came in much earlier releases. Option c suggests that iOS 9 removed touch and required hardware keyboards, which is contrary to the entire design of iOS. Option d talks about the removal of multitasking and background refresh, which is the opposite of what iOS 9 delivered.

Common Pitfalls:
Candidates sometimes confuse feature timelines or assume that any new feature they remember appeared in the most recent version they used. A good habit is to associate each major iOS version with one or two signature features: for iOS 9, think iPad multitasking and Proactive Siri. This mental map helps you answer version specific questions quickly.

Final Answer:
The correct summary is that iOS 9 introduced features such as split screen and slide over multitasking on supported iPads, Proactive Siri suggestions, improved Notes and Maps with transit directions, and better performance and battery optimisation.