Exchange rates and tariffs are associated with international sourcing.
The other options are concerns for both local sourcing and international sourcing.

This is sole sourcing as there is only one supplier in the marketplace.
Be careful not to confuse single sourcing and sole sourcing. Single sourcing is when a buyer chooses to work with only one supplier (usually to achieve economies of scale), sole sourcing, on the other hand, is when the buyer doesn't have a choice- they work with one supplier because there is only one supplier in the market.
Types of sourcing is a key concept for this exam.

"yes- ethics and sustainability form part of 'value for money' " is the correct answer.
There are several factors that represent value for money and these are listed on p.3. These include; price, delivery, quality, ethics, sustainability and availability.

The correct answers are 'it is easy to drive down costs' (as you can pit the suppliers against each other) and
'low risk of failure to supply' (if one supplier can't provide what you need, the other supplier might be able to).
Economies of scale and supplier loyalty are advantages of single-sourcing.
There is a risk of failure to supply is a risk associated with single sourcing.
There's a useful table of advantages and disadvantages of single / multi sourcing on p.22. Types of sourcing is a key topic for the exam.