Here are the answers for the closest meanings to the underlined words:

IV. Choose the answer A, B, C or D which indicates the word CLOSEST in meaning to the underlined word.

1. **challenging** - A. easy (incorrect), B. peaceful (incorrect), C. boring (incorrect), **D. hard (correct)**

2. **user-friendly** - A. hard to use (incorrect), **B. easy to use (correct)**, C. hard to understand (incorrect), D. easy to understand (incorrect)

3. **Focus** - A. Concentrate on (correct), **B. Ignore (incorrect)**, C. Respect (incorrect), D. Practice (incorrect)

V. Choose the answer A, B, C or D which indicates the word OPPOSITE in meaning to the underlined word.

1. **get along with** - A. mix with (incorrect), B. fall apart (correct), C. connect with (incorrect), D. get on with (incorrect)

2. **logged on** - A. sign in (incorrect), **B. logged in to (correct)**, C. sign in to (incorrect), D. logged out of (incorrect)

3. **stressed** - A. pressured (correct), B. focused (incorrect), C. disliked (incorrect), **D. relaxed (incorrect)**

So, the final answers are:
IV: 1-D, 2-B, 3-A
V: 1-B, 2-D, 3-A