Here you’ve got the answers:
1-a-true
2-a-black
3-c-picadilly
4-b-the serpentine
5-c-buckingham palace
6-c-nelson
7-c-london bridge and tower bridge
8-a-regents park
9-b-tate modern
10-a-kensington gardens
11-d-black
12-a-hyde park
13-b-whitehall
14-a-beefeaters
15-c-oxford street
16-c-all of them
17-d-northern line
18-b-waxworks
19-a-globe
20-b-eros
21-b-a cathedral