49 CFR 195, 195.410 Line markers are not required for:

According to 49 CFR 195.410(b), line markers are not required for pipelines located:

• (1) Offshore or under inland navigable waters.
• (2) In heavily developed urban areas where the placement of markers is impractical and would not serve the purpose for which markers are intended.
• (3) In an area where a damage prevention program is in effect under § 195.440.
• (4) In an area where the pipeline is clearly visible and its presence is otherwise indicated.

• Option a: "Offshore or at crossings of or under waterways and other bodies of water." This aligns with 49 CFR 195.410(b)(1).
• Option b: "Wetlands." Wetlands are not explicitly listed as a general exception in 49 CFR 195.410(b).
• Option c: "In heavily developed urban areas such as downtown business centers where the placement of markers would not serve the purpose for which markers are intended." This aligns with 49 CFR 195.410(b)(2).
• Option d: "a) and c) above." Since both a and c are valid exceptions, this option combines them.

Both conditions described in options a and c are indeed situations where line markers are not required under 49 CFR 195.410.

The final answer is $\boxed{\text{d) a) and c) above}}$.