What is topology?

I- Topology is a branch of mathematics that studies the properties of objects that do not change under continuous transformations, such as stretching or bending.
II- Topology has applications in various fields, such as genetics, physics, chemistry, and computer science.
III- Topologists are particularly interested in the study of varieties, which suggests a multiplicity of forms.
IV- The study of knots and their invariants is one of the main topics of topology.
a) Only I and II are correct.
b) Only II and III are correct.
c) Only III and IV are correct.
d) All statements are correct.