Curve

Start with Curve basic shape
Curves Basic Shapes * Click On the images to enlarger

1. Go to Create panel > Standard Primitive > Sphere, set the radius for example = 2 cm and the segments = 6 > Right Click > Convert To Editable Poly

2.Go to Modify Panel > Polygon Selection > Select some Polygons > Delete Unnecessary Polygon

3. Rotate Sphere a bit then  go to Modify Panel > Editable Poly > Edge Selection > Select one Edge > Extrude Edge ( Click edge + press "Shift" on your Keyboard + Move )

4. Go to Modify Panel > Editable Poly > Vertex selection > Select one Vertex > Right Click > Remove

5. Extrude Edge ( see point number 3 above ) then go to Modify Panel > Vertex selection > Click "Target weld" button > click first vertex then click vertex target to weld it.

6. Go to modify Panel > Edge selection  > Extrude Edges ( Click edge + press "Shift" on your Keyboard + Move )  you just need  2 combination tools "Move" and "Rotate" to do this.

7. Go to  Modify Panel > Edge Selection > Target Weld > Click first Edge then click edge target to
weld these Edges

8. Go to  Modify Panel > Vertex Selection > "Cut" > Click first point then click another point to make new lines.

9. Go to Modify Panel > Edge Selection > Select some Edges ( you can use "Loop" selection, or just simply  do "double click" on first edge it will automatically select the rest ) > Pull Edges

10. Go to Modify Panel > Edge Selection > Select first edge then click "Ring"to select quickly > "Connect" to add more lines.

11. Go to Modify Panel > Editable Poly > Subdivision Surface > activate "Use Nurms Subdivision" set the iterations = 2 or more to get the smooth object. also you can do with "Mesh smooth, Turbo Smooth, or Open Subdiv Modifier"

12. Final