Final answer:
To enable Private Browsing in Safari on an iPhone, open Safari, tap the pages icon, and select 'Private'. There is no universal 'Private Mode' for the entire iPhone, and for privacy in other areas, you need to adjust specific settings like turning off Location Services. For taking private photos, use the Photos app to hide sensitive images.
Step-by-step explanation:
To put your iPhone on private mode, typically you would be looking for a way to browse the internet without saving your browsing history. This is often referred to as 'Private Browsing' and is a feature in the Safari browser. None of the options a) through d) directly describe how to enable a general 'Private Mode' on the iPhone, as Private Mode is not a universal setting across the phone, but you can enable 'Private Browsing' in Safari. To do this, open Safari, then tap the two-squared icon at the bottom right to view your open pages. Here, you can choose 'Private' to open a private browsing session. For privacy in other apps, you might employ different settings (like turning off 'Location Services' in Settings, then Privacy, for example).
If, on the other hand, you're referring to taking private photos or creating silhouettes without others seeing, you may want to use the Photos app. Within the Photos app, you can select photos, tap 'Share', and choose 'Hide' to place sensitive photos in a hidden album. However, for professional silhouette photography tips for your iPhone, visiting reliable online tutorials can be quite beneficial.