Which transactions will not cause change in current ratio

Question

A company has a current ratio of 2:1 at December 31, 2014. Which of the following transactions will not cause a change in the current ratio?

1. Declaration of a 10% stock dividend.
2. Purchase of short-term investments for cash.
3. Payment of a long-term liability.
4. Declaration of a cash dividend.
5. Both a. and b.
6. Both a. and d.