Please help ASAP! Which of the 4 strategies is best and why?

1) Curved sea walls

2)Rock Armour

3)Beach replenishment

4)Nothing Coastal Management

Simple astronomical telescope the objective lens has a focal length of 75 cm and that of a piece of 5cm of the lenses are 18 cm apart when will be final image of a distant object before

Asap! ! ! ! true or false the gobi desert, the largest desert in asia. covers parts of northern china and southern russia

Which statement about this figure is false