1、D

2. Omission

3、24

4, 20 cm

5. The left view is omitted. The geometric shape is a straight triangular prism.

Group b

6、r = 1/4R

7. (1)14.4m.

(2)48?

Group c

8, blue, yellow

9. From △OCP ∽ △ECA, OP/EA = CP/CA, that is, OP/2 = (1+AP)/ 1 ①.

From △ODP ∽ △FDB, OP/FB = DP/DB, that is, OP/2 = (4.8+AP)/ 1.8 ②.

According to ① and ②, OP = 9.5, that is, the height of street lamp is 9.5m..

Bian Xiao suggested: