In initial tunnel route surveys for civil engineering projects, arrange the activities in the correct order: (1) mark the portal point with concrete pillars on ground, (2) mark tunnel obligatory points on topographical maps, (3) perform preliminary setting of the tunnel on Survey of India topographical maps, and (4) drive (join) control lines between the fixed obligatory points.

Introduction / Context:
Tunnel planning begins long before excavation. An orderly initial survey sequence ensures that the alignment is first conceptualized on authoritative maps, refined by fixing obligatory control points (e.g., portals, shafts, curve points), physically connected by lines on the map and ground, and finally materialized at the site with permanent markers. This question checks understanding of that logical progression from desk study to field control.

Given Data / Assumptions:

• Four activities are listed and must be sequenced.
• Survey of India maps are the standard base for preliminary alignment.
• Obligatory points are critical control points governing line and grade.
• Portal points are materialized on ground with concrete pillars for durability.

Concept / Approach:

Good practice is to start with map-based preliminary setting to decide a viable corridor. Then, obligatory points are marked on the topo sheets. Next, the surveyor establishes control/connection between these fixed points by driving lines (joining them). Finally, the alignment is pegged on ground at the portal with permanent concrete pillars to serve as lasting benchmarks for subsequent detailed survey and construction layout.

Step-by-Step Solution:

Verification / Alternative check:

Reversing the order would either attempt to pillar a portal before the alignment is fixed, or join points that are not yet defined—both illogical. The selected sequence mirrors standard feasibility-to-field-transfer workflow.

Why Other Options Are Wrong:

• 1 2 3 4: Starts construction marking before map-based decisions.
• 4 3 1 2 or 2 4 3 1: Join or mark elements before preliminary map setting—procedure is inverted.
• Any other order breaks the conceptual-to-physical progression.

Common Pitfalls:

• Confusing “driving lines” on map versus staking on ground; here it refers to joining fixed points for control.
• Fixing portals prematurely without confirmed alignment.

Final Answer:

3 2 4 1