Why does churchill believe an invasion of british soil is not likely to occur in the near future?

Answer choices to this question are:

A. Because the enemy would have to cross the heavily guarded sea to get there.
B. Because the enemy would have to get past the French army. 
C. Because the enemy did not have enough foot soldiers to invade by ground.D. Because the enemy did not have a strong enough air force.

Correct Answer choice is:

A. Because the enemy would have to cross the heavily guarded sea to get there.

Explanation:
British naval forces created a strong barrier in the ocean to defense their enemy and it was not that easy to break the barrier and invade the region.  If the Germans launched an invasion they would have failed as it was their weaknesses in sea power compared to the British Navy.