1.
The bases are on the (interior/exterior) of the double helix.
2.
They are arranged (randomly/neatly stacked).
3.
The phosphate groups are on the (interior/exterior) of the DNA molecule.
4.
The sugar groups on the (interior/exterior) of the DNA molecule.

1. The bases are on the interior of the double helix.

2.  They are arranged neatly stacked.

3.  The phosphate groups are on the exterior of the DNA molecule.

4.  The sugar groups on the exterior of the DNA molecule.

Explanation:

DNA is made up of basic chemical components called nucleotides. These basic components include a phosphate group, a sugar group and one of four types of alternative nitrogenous bases. To form a strand of DNA, the nucleotides unite to form chains, alternating with the phosphate and sugar groups.  

The four types of nitrogenous bases found in nucleotides are: adenine (A), thymine (T), guanine (G), and cytosine (C). The order, or sequence, of these bases determines which biological instructions are contained in a strand of DNA, being within the strands already mentioned.

indicate valleys, hills, steepness and gentleness of slopes.

explanation:

contour lines on a map indicate elevation, or depth. numeric notations on contour lines refer to the level of elevation, or height about sea level.